diff --git a/.cargo-husky/hooks/pre-push b/.cargo-husky/hooks/pre-push
index a1e3616f..50105aa1 100755
--- a/.cargo-husky/hooks/pre-push
+++ b/.cargo-husky/hooks/pre-push
@@ -1,5 +1,7 @@
 #!/bin/sh
 
+set -e
+
 echo "Running pre-push hook:"
 
 echo "Executing: cargo +nightly clippy -- -D clippy::all"
diff --git a/.vscode/settings.json b/.vscode/settings.json
index 8653ef8a..9a9b4df4 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -46,10 +46,13 @@
         "fract",
         "gnueabihf",
         "gotop",
+        "gotop's",
         "gtop",
         "haase",
         "heim",
         "hjkl",
+        "htop",
+        "indexmap",
         "libc",
         "markdownlint",
         "memb",
@@ -62,6 +65,7 @@
         "nvme",
         "paren",
         "pmem",
+        "ppid",
         "prepush",
         "processthreadsapi",
         "regexes",
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9b3357bd..2fbcb362 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - [#220](https://github.com/ClementTsang/bottom/pull/220): Add ability to hide specific temperature and disk entries via config.
 
+- [#223](https://github.com/ClementTsang/bottom/pull/223): Add tree mode for processes.
+
 ### Changes
 
 - [#213](https://github.com/ClementTsang/bottom/pull/213), [#214](https://github.com/ClementTsang/bottom/pull/214): Updated help descriptions, added auto-complete generation.
diff --git a/Cargo.lock b/Cargo.lock
index 20f2221f..7893cdbb 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -150,6 +150,7 @@ dependencies = [
  "fern",
  "futures",
  "heim",
+ "indexmap",
  "itertools",
  "lazy_static",
  "libc",
@@ -534,6 +535,12 @@ version = "0.21.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bcc8e0c9bce37868955864dbecd2b1ab2bdf967e6f28066d65aaac620444b65c"
 
+[[package]]
+name = "hashbrown"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "00d63df3d41950fb462ed38308eea019113ad1508da725bbedcd0fa5a85ef5f7"
+
 [[package]]
 name = "heim"
 version = "0.0.10"
@@ -723,6 +730,16 @@ version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "023b39be39e3a2da62a94feb433e91e8bcd37676fbc8bea371daf52b7a769a3e"
 
+[[package]]
+name = "indexmap"
+version = "1.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "55e2e4c765aa53a0424761bf9f41aa7a6ac1efa87238f59560640e27fca028f2"
+dependencies = [
+ "autocfg",
+ "hashbrown",
+]
+
 [[package]]
 name = "iovec"
 version = "0.1.4"
diff --git a/Cargo.toml b/Cargo.toml
index d8a83071..d2ec0dd0 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -32,6 +32,7 @@ ctrlc = {version = "3.1", features = ["termination"]}
 clap = "2.33"
 dirs = "3.0.1"
 futures = "0.3.5"
+indexmap = "1.6.0"
 itertools = "0.9.0"
 libc = "0.2"
 regex = "1.3"
diff --git a/README.md b/README.md
index e504ea58..aa38c6a0 100644
--- a/README.md
+++ b/README.md
@@ -41,6 +41,7 @@ A cross-platform graphical process/system monitor with a customizable interface
   - [Processes](#processes)
     - [Process searching](#process-searching)
     - [Process sorting](#process-sorting)
+    - [Tree mode](#tree-mode)
   - [Zoom](#zoom)
   - [Expanding](#expanding)
   - [Basic mode](#basic-mode)
@@ -246,23 +247,24 @@ Run using `btm`.
 | `s, F6`       | Open process sort widget                                         |
 | `I`           | Invert current sort                                              |
 | `%`           | Toggle between values and percentages for memory usage           |
+| `t`, `F5`     | Toggle tree mode                                                 |
 
 #### Process search bindings
 
-|              |                                              |
-| ------------ | -------------------------------------------- |
-| `Tab`        | Toggle between searching by PID or name      |
-| `Esc`        | Close the search widget (retains the filter) |
-| `Ctrl-a`     | Skip to the start of the search query        |
-| `Ctrl-e`     | Skip to the end of the search query          |
-| `Ctrl-u`     | Clear the current search query               |
-| `Backspace`  | Delete the character behind the cursor       |
-| `Delete`     | Delete the character at the cursor           |
-| `Alt-c`/`F1` | Toggle matching case                         |
-| `Alt-w`/`F2` | Toggle matching the entire word              |
-| `Alt-r`/`F3` | Toggle using regex                           |
-| `Left`       | Move cursor left                             |
-| `Right`      | Move cursor right                            |
+|               |                                              |
+| ------------- | -------------------------------------------- |
+| `Tab`         | Toggle between searching by PID or name      |
+| `Esc`         | Close the search widget (retains the filter) |
+| `Ctrl-a`      | Skip to the start of the search query        |
+| `Ctrl-e`      | Skip to the end of the search query          |
+| `Ctrl-u`      | Clear the current search query               |
+| `Backspace`   | Delete the character behind the cursor       |
+| `Delete`      | Delete the character at the cursor           |
+| `Alt-c`, `F1` | Toggle matching case                         |
+| `Alt-w`, `F2` | Toggle matching the entire word              |
+| `Alt-r`, `F3` | Toggle using regex                           |
+| `Left`        | Move cursor left                             |
+| `Right`       | Move cursor right                            |
 
 ### Process sort bindings
 
@@ -424,6 +426,23 @@ You can sort the processes list by any column you want by pressing `s` while on
 
 ![sorting](assets/sort.png)
 
+#### Tree mode
+
+Use `t` or `F5` to toggle tree mode in a process widget. This is somewhat similar to htop's tree
+mode.
+
+![Standard tree](assets/trees_1.png)
+
+Sorting works as well, but it is done per groups of siblings. For example, by CPU%:
+
+![Standard tree](assets/trees_2.png)
+
+You can also still filter processes. Branches that entirely do not match the query are pruned out,
+but if a branch contains an element that does match the query, any non-matching elements will instead
+just be greyed out, so the tree structure is still maintained:
+
+![Standard tree](assets/trees_3.png)
+
 ### Zoom
 
 Using the `+`/`-` keys or the scroll wheel will move the current time intervals of the currently selected widget, and `=` to reset the zoom levels to the default.
diff --git a/assets/trees_1.png b/assets/trees_1.png
new file mode 100644
index 00000000..cfe7e6b2
Binary files /dev/null and b/assets/trees_1.png differ
diff --git a/assets/trees_2.png b/assets/trees_2.png
new file mode 100644
index 00000000..e6c1063c
Binary files /dev/null and b/assets/trees_2.png differ
diff --git a/assets/trees_3.png b/assets/trees_3.png
new file mode 100644
index 00000000..741116b1
Binary files /dev/null and b/assets/trees_3.png differ
diff --git a/src/app.rs b/src/app.rs
index 1aa390f7..4d07f4d0 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -13,6 +13,7 @@ pub use states::*;
 use crate::{
     canvas, constants,
     utils::error::{BottomError, Result},
+    Pid,
 };
 
 pub mod data_farmer;
@@ -67,7 +68,7 @@ pub struct App {
     pub dd_err: Option<String>,
 
     #[builder(default, setter(skip))]
-    to_delete_process_list: Option<(String, Vec<u32>)>,
+    to_delete_process_list: Option<(String, Vec<Pid>)>,
 
     #[builder(default = false, setter(skip))]
     pub is_frozen: bool,
@@ -265,37 +266,40 @@ impl App {
                         .proc_state
                         .get_mut_widget_state(self.current_widget.widget_id)
                     {
-                        // Toggles process widget grouping state
-                        proc_widget_state.is_grouped = !(proc_widget_state.is_grouped);
+                        // Do NOT allow when in tree mode!
+                        if !proc_widget_state.is_tree_mode {
+                            // Toggles process widget grouping state
+                            proc_widget_state.is_grouped = !(proc_widget_state.is_grouped);
 
-                        // Forcefully switch off column if we were on it...
-                        if (proc_widget_state.is_grouped
-                            && proc_widget_state.process_sorting_type
-                                == data_harvester::processes::ProcessSorting::Pid)
-                            || (!proc_widget_state.is_grouped
+                            // Forcefully switch off column if we were on it...
+                            if (proc_widget_state.is_grouped
                                 && proc_widget_state.process_sorting_type
-                                    == data_harvester::processes::ProcessSorting::Count)
-                        {
-                            proc_widget_state.process_sorting_type =
-                                data_harvester::processes::ProcessSorting::CpuPercent; // Go back to default, negate PID for group
-                            proc_widget_state.process_sorting_reverse = true;
+                                    == data_harvester::processes::ProcessSorting::Pid)
+                                || (!proc_widget_state.is_grouped
+                                    && proc_widget_state.process_sorting_type
+                                        == data_harvester::processes::ProcessSorting::Count)
+                            {
+                                proc_widget_state.process_sorting_type =
+                                    data_harvester::processes::ProcessSorting::CpuPercent; // Go back to default, negate PID for group
+                                proc_widget_state.is_process_sort_descending = true;
+                            }
+
+                            proc_widget_state
+                                .columns
+                                .column_mapping
+                                .get_mut(&processes::ProcessSorting::State)
+                                .unwrap()
+                                .enabled = !(proc_widget_state.is_grouped);
+
+                            proc_widget_state
+                                .columns
+                                .toggle(&processes::ProcessSorting::Count);
+                            proc_widget_state
+                                .columns
+                                .toggle(&processes::ProcessSorting::Pid);
+
+                            self.proc_state.force_update = Some(self.current_widget.widget_id);
                         }
-
-                        proc_widget_state
-                            .columns
-                            .column_mapping
-                            .get_mut(&processes::ProcessSorting::State)
-                            .unwrap()
-                            .enabled = !(proc_widget_state.is_grouped);
-
-                        proc_widget_state
-                            .columns
-                            .toggle(&processes::ProcessSorting::Count);
-                        proc_widget_state
-                            .columns
-                            .toggle(&processes::ProcessSorting::Pid);
-
-                        self.proc_state.force_update = Some(self.current_widget.widget_id);
                     }
                 }
                 _ => {}
@@ -384,8 +388,8 @@ impl App {
                     };
 
                 if let Some(proc_widget_state) = self.proc_state.get_mut_widget_state(widget_id) {
-                    proc_widget_state.process_sorting_reverse =
-                        !proc_widget_state.process_sorting_reverse;
+                    proc_widget_state.is_process_sort_descending =
+                        !proc_widget_state.is_process_sort_descending;
 
                     self.proc_state.force_update = Some(widget_id);
                 }
@@ -483,6 +487,24 @@ impl App {
         }
     }
 
+    pub fn toggle_tree_mode(&mut self) {
+        if let Some(proc_widget_state) = self
+            .proc_state
+            .widget_states
+            .get_mut(&(self.current_widget.widget_id))
+        {
+            proc_widget_state.is_tree_mode = !proc_widget_state.is_tree_mode;
+
+            if proc_widget_state.is_tree_mode {
+                // We enabled... set PID sort type to ascending.
+                proc_widget_state.process_sorting_type = processes::ProcessSorting::Pid;
+                proc_widget_state.is_process_sort_descending = false;
+            }
+
+            self.proc_state.force_update = Some(self.current_widget.widget_id);
+        }
+    }
+
     /// One of two functions allowed to run while in a dialog...
     pub fn on_enter(&mut self) {
         if self.delete_dialog_state.is_showing_dd {
@@ -889,7 +911,7 @@ impl App {
                 if proc_widget_state.scroll_state.current_scroll_position
                     < corresponding_filtered_process_list.len()
                 {
-                    let current_process: (String, Vec<u32>);
+                    let current_process: (String, Vec<Pid>);
                     if self.is_grouped(self.current_widget.widget_id) {
                         if let Some(process) = &corresponding_filtered_process_list
                             .get(proc_widget_state.scroll_state.current_scroll_position)
@@ -1069,13 +1091,13 @@ impl App {
                     {
                         match proc_widget_state.process_sorting_type {
                             processes::ProcessSorting::CpuPercent => {
-                                proc_widget_state.process_sorting_reverse =
-                                    !proc_widget_state.process_sorting_reverse
+                                proc_widget_state.is_process_sort_descending =
+                                    !proc_widget_state.is_process_sort_descending
                             }
                             _ => {
                                 proc_widget_state.process_sorting_type =
                                     processes::ProcessSorting::CpuPercent;
-                                proc_widget_state.process_sorting_reverse = true;
+                                proc_widget_state.is_process_sort_descending = true;
                             }
                         }
                         self.proc_state.force_update = Some(self.current_widget.widget_id);
@@ -1092,13 +1114,13 @@ impl App {
                     {
                         match proc_widget_state.process_sorting_type {
                             processes::ProcessSorting::MemPercent => {
-                                proc_widget_state.process_sorting_reverse =
-                                    !proc_widget_state.process_sorting_reverse
+                                proc_widget_state.is_process_sort_descending =
+                                    !proc_widget_state.is_process_sort_descending
                             }
                             _ => {
                                 proc_widget_state.process_sorting_type =
                                     processes::ProcessSorting::MemPercent;
-                                proc_widget_state.process_sorting_reverse = true;
+                                proc_widget_state.is_process_sort_descending = true;
                             }
                         }
                         self.proc_state.force_update = Some(self.current_widget.widget_id);
@@ -1116,13 +1138,13 @@ impl App {
                         if !proc_widget_state.is_grouped {
                             match proc_widget_state.process_sorting_type {
                                 processes::ProcessSorting::Pid => {
-                                    proc_widget_state.process_sorting_reverse =
-                                        !proc_widget_state.process_sorting_reverse
+                                    proc_widget_state.is_process_sort_descending =
+                                        !proc_widget_state.is_process_sort_descending
                                 }
                                 _ => {
                                     proc_widget_state.process_sorting_type =
                                         processes::ProcessSorting::Pid;
-                                    proc_widget_state.process_sorting_reverse = false;
+                                    proc_widget_state.is_process_sort_descending = false;
                                 }
                             }
                             self.proc_state.force_update = Some(self.current_widget.widget_id);
@@ -1168,8 +1190,8 @@ impl App {
                         match proc_widget_state.process_sorting_type {
                             processes::ProcessSorting::ProcessName
                             | processes::ProcessSorting::Command => {
-                                proc_widget_state.process_sorting_reverse =
-                                    !proc_widget_state.process_sorting_reverse
+                                proc_widget_state.is_process_sort_descending =
+                                    !proc_widget_state.is_process_sort_descending
                             }
                             _ => {
                                 proc_widget_state.process_sorting_type =
@@ -1178,7 +1200,7 @@ impl App {
                                     } else {
                                         processes::ProcessSorting::ProcessName
                                     };
-                                proc_widget_state.process_sorting_reverse = false;
+                                proc_widget_state.is_process_sort_descending = false;
                             }
                         }
                         self.proc_state.force_update = Some(self.current_widget.widget_id);
@@ -1194,6 +1216,7 @@ impl App {
             'L' | 'D' => self.move_widget_selection(&WidgetDirection::Right),
             'K' | 'W' => self.move_widget_selection(&WidgetDirection::Up),
             'J' | 'S' => self.move_widget_selection(&WidgetDirection::Down),
+            't' => self.toggle_tree_mode(),
             '+' => self.zoom_in(),
             '-' => self.zoom_out(),
             '=' => self.reset_zoom(),
@@ -1228,7 +1251,7 @@ impl App {
         }
     }
 
-    pub fn get_to_delete_processes(&self) -> Option<(String, Vec<u32>)> {
+    pub fn get_to_delete_processes(&self) -> Option<(String, Vec<Pid>)> {
         self.to_delete_process_list.clone()
     }
 
diff --git a/src/app/data_harvester.rs b/src/app/data_harvester.rs
index eb5b0add..e7deca52 100644
--- a/src/app/data_harvester.rs
+++ b/src/app/data_harvester.rs
@@ -72,7 +72,7 @@ pub struct DataCollector {
     pub data: Data,
     sys: System,
     #[cfg(target_os = "linux")]
-    pid_mapping: HashMap<u32, processes::PrevProcDetails>,
+    pid_mapping: HashMap<crate::Pid, processes::PrevProcDetails>,
     #[cfg(target_os = "linux")]
     prev_idle: f64,
     #[cfg(target_os = "linux")]
diff --git a/src/app/data_harvester/processes.rs b/src/app/data_harvester/processes.rs
index dcd6d647..8604bf8f 100644
--- a/src/app/data_harvester/processes.rs
+++ b/src/app/data_harvester/processes.rs
@@ -1,3 +1,4 @@
+use crate::Pid;
 use std::path::PathBuf;
 use sysinfo::ProcessStatus;
 
@@ -59,7 +60,8 @@ impl Default for ProcessSorting {
 
 #[derive(Debug, Clone, Default)]
 pub struct ProcessHarvest {
-    pub pid: u32,
+    pub pid: Pid,
+    pub parent_pid: Option<Pid>, // Remember, parent_pid 0 is root...
     pub cpu_usage_percent: f64,
     pub mem_usage_percent: f64,
     pub mem_usage_bytes: u64,
@@ -89,7 +91,7 @@ pub struct PrevProcDetails {
 }
 
 impl PrevProcDetails {
-    pub fn new(pid: u32) -> Self {
+    pub fn new(pid: Pid) -> Self {
         PrevProcDetails {
             proc_io_path: PathBuf::from(format!("/proc/{}/io", pid)),
             proc_exe_path: PathBuf::from(format!("/proc/{}/exe", pid)),
@@ -200,7 +202,7 @@ fn read_path_contents(path: &PathBuf) -> std::io::Result<String> {
 
 #[cfg(target_os = "linux")]
 fn get_linux_process_state(stat: &[&str]) -> (char, String) {
-    // The -2 offset is because of us cutting off name + pid
+    // The -2 offset is because of us cutting off name + pid, normally it's 2
     if let Some(first_char) = stat[0].chars().collect::<Vec<char>>().first() {
         (
             *first_char,
@@ -241,8 +243,8 @@ fn get_linux_cpu_usage(
 #[allow(clippy::too_many_arguments)]
 #[cfg(target_os = "linux")]
 fn read_proc<S: core::hash::BuildHasher>(
-    pid: u32, cpu_usage: f64, cpu_fraction: f64,
-    pid_mapping: &mut HashMap<u32, PrevProcDetails, S>, use_current_cpu_total: bool,
+    pid: Pid, cpu_usage: f64, cpu_fraction: f64,
+    pid_mapping: &mut HashMap<Pid, PrevProcDetails, S>, use_current_cpu_total: bool,
     time_difference_in_secs: u64, mem_total_kb: u64, page_file_kb: u64,
 ) -> error::Result<ProcessHarvest> {
     let pid_stat = pid_mapping
@@ -282,6 +284,7 @@ fn read_proc<S: core::hash::BuildHasher>(
         &mut pid_stat.cpu_time,
         use_current_cpu_total,
     )?;
+    let parent_pid = stat[1].parse::<Pid>().ok();
     let (_vsize, rss) = get_linux_process_vsize_rss(&stat);
     let mem_usage_kb = rss * page_file_kb;
     let mem_usage_percent = mem_usage_kb as f64 / mem_total_kb as f64 * 100.0;
@@ -320,6 +323,7 @@ fn read_proc<S: core::hash::BuildHasher>(
 
     Ok(ProcessHarvest {
         pid,
+        parent_pid,
         name,
         command,
         mem_usage_percent,
@@ -337,14 +341,16 @@ fn read_proc<S: core::hash::BuildHasher>(
 #[cfg(target_os = "linux")]
 pub fn linux_get_processes_list(
     prev_idle: &mut f64, prev_non_idle: &mut f64,
-    pid_mapping: &mut HashMap<u32, PrevProcDetails, RandomState>, use_current_cpu_total: bool,
+    pid_mapping: &mut HashMap<Pid, PrevProcDetails, RandomState>, use_current_cpu_total: bool,
     time_difference_in_secs: u64, mem_total_kb: u64, page_file_kb: u64,
 ) -> crate::utils::error::Result<Vec<ProcessHarvest>> {
+    // TODO: [PROC THREADS] Add threads
+
     if let Ok((cpu_usage, cpu_fraction)) = cpu_usage_calculation(prev_idle, prev_non_idle) {
         let process_vector: Vec<ProcessHarvest> = std::fs::read_dir("/proc")?
             .filter_map(|dir| {
                 if let Ok(dir) = dir {
-                    let pid = dir.file_name().to_string_lossy().trim().parse::<u32>();
+                    let pid = dir.file_name().to_string_lossy().trim().parse::<Pid>();
                     if let Ok(pid) = pid {
                         // I skip checking if the path is also a directory, it's not needed I think?
                         if let Ok(process_object) = read_proc(
@@ -424,7 +430,8 @@ pub fn windows_macos_get_processes_list(
         let disk_usage = process_val.disk_usage();
 
         process_vector.push(ProcessHarvest {
-            pid: process_val.pid() as u32,
+            pid: process_val.pid(),
+            parent_pid: process_val.parent(),
             name,
             command,
             mem_usage_percent: if mem_total_kb > 0 {
diff --git a/src/app/process_killer.rs b/src/app/process_killer.rs
index cb0662bc..e367d99c 100644
--- a/src/app/process_killer.rs
+++ b/src/app/process_killer.rs
@@ -10,6 +10,7 @@ use winapi::{
 
 /// This file is meant to house (OS specific) implementations on how to kill processes.
 use crate::utils::error::BottomError;
+use crate::Pid;
 
 #[cfg(target_os = "windows")]
 struct Process(HANDLE);
@@ -31,9 +32,9 @@ impl Process {
 }
 
 /// Kills a process, given a PID.
-pub fn kill_process_given_pid(pid: u32) -> crate::utils::error::Result<()> {
-    if cfg!(target_os = "linux") || cfg!(target_os = "macos") {
-        #[cfg(any(target_os = "linux", target_os = "macos"))]
+pub fn kill_process_given_pid(pid: Pid) -> crate::utils::error::Result<()> {
+    if cfg!(target_family = "unix") {
+        #[cfg(any(target_family = "unix"))]
         {
             let output = unsafe { libc::kill(pid as i32, libc::SIGTERM) };
             if output != 0 {
@@ -59,8 +60,8 @@ pub fn kill_process_given_pid(pid: u32) -> crate::utils::error::Result<()> {
                 };
             }
         }
-    } else if cfg!(target_os = "windows") {
-        #[cfg(target_os = "windows")]
+    } else if cfg!(target_family = "windows") {
+        #[cfg(target_family = "windows")]
         {
             let process = Process::open(pid as DWORD)?;
             process.kill()?;
diff --git a/src/app/states.rs b/src/app/states.rs
index cf9123db..318b2175 100644
--- a/src/app/states.rs
+++ b/src/app/states.rs
@@ -9,6 +9,7 @@ use crate::{
     constants,
     data_harvester::processes::{self, ProcessSorting},
 };
+use ProcessSorting::*;
 
 #[derive(Debug)]
 pub enum ScrollDirection {
@@ -159,7 +160,6 @@ pub struct ProcColumn {
 
 impl Default for ProcColumn {
     fn default() -> Self {
-        use ProcessSorting::*;
         let ordered_columns = vec![
             Count,
             Pid,
@@ -352,11 +352,12 @@ pub struct ProcWidgetState {
     pub is_grouped: bool,
     pub scroll_state: AppScrollWidgetState,
     pub process_sorting_type: processes::ProcessSorting,
-    pub process_sorting_reverse: bool,
+    pub is_process_sort_descending: bool,
     pub is_using_command: bool,
     pub current_column_index: usize,
     pub is_sort_open: bool,
     pub columns: ProcColumn,
+    pub is_tree_mode: bool,
 }
 
 impl ProcWidgetState {
@@ -390,11 +391,12 @@ impl ProcWidgetState {
             is_grouped,
             scroll_state: AppScrollWidgetState::default(),
             process_sorting_type,
-            process_sorting_reverse: true,
+            is_process_sort_descending: true,
             is_using_command: false,
             current_column_index: 0,
             is_sort_open: false,
             columns,
+            is_tree_mode: false,
         }
     }
 
@@ -422,7 +424,7 @@ impl ProcWidgetState {
         if let Some(new_sort_type) = self.columns.ordered_columns.get(true_index) {
             if *new_sort_type == self.process_sorting_type {
                 // Just reverse the search if we're reselecting!
-                self.process_sorting_reverse = !(self.process_sorting_reverse);
+                self.is_process_sort_descending = !(self.is_process_sort_descending);
             } else {
                 self.process_sorting_type = new_sort_type.clone();
                 match self.process_sorting_type {
@@ -431,7 +433,7 @@ impl ProcWidgetState {
                     | ProcessSorting::ProcessName
                     | ProcessSorting::Command => {
                         // Also invert anything that uses alphabetical sorting by default.
-                        self.process_sorting_reverse = false;
+                        self.is_process_sort_descending = false;
                     }
                     _ => {}
                 }
diff --git a/src/canvas.rs b/src/canvas.rs
index 61f74e4f..e276e097 100644
--- a/src/canvas.rs
+++ b/src/canvas.rs
@@ -42,7 +42,6 @@ pub struct DisplayableData {
     pub disk_data: Vec<Vec<String>>,
     pub temp_sensor_data: Vec<Vec<String>>,
     pub single_process_data: Vec<ConvertedProcessData>, // Contains single process data
-    pub process_data: Vec<ConvertedProcessData>, // Not the final value, may be grouped or single
     pub finalized_process_data_map: HashMap<u64, Vec<ConvertedProcessData>>, // What's actually displayed
     pub mem_label_percent: String,
     pub swap_label_percent: String,
diff --git a/src/canvas/canvas_colours.rs b/src/canvas/canvas_colours.rs
index 98932d5d..2876e24b 100644
--- a/src/canvas/canvas_colours.rs
+++ b/src/canvas/canvas_colours.rs
@@ -28,6 +28,7 @@ pub struct CanvasColours {
     // Full, Medium, Low
     pub battery_bar_styles: Vec<Style>,
     pub invalid_query_style: Style,
+    pub disabled_text_style: Style,
 }
 
 impl Default for CanvasColours {
@@ -63,7 +64,8 @@ impl Default for CanvasColours {
                 Style::default().fg(Color::Green),
                 Style::default().fg(Color::Green),
             ],
-            invalid_query_style: tui::style::Style::default().fg(tui::style::Color::Red),
+            invalid_query_style: Style::default().fg(tui::style::Color::Red),
+            disabled_text_style: Style::default().fg(Color::DarkGray),
         }
     }
 }
diff --git a/src/canvas/widgets/cpu_graph.rs b/src/canvas/widgets/cpu_graph.rs
index e000b66f..86999345 100644
--- a/src/canvas/widgets/cpu_graph.rs
+++ b/src/canvas/widgets/cpu_graph.rs
@@ -349,13 +349,11 @@ impl CpuGraphWidget for Painter {
                 get_variable_intrinsic_widths(width as u16, &width_ratios, &CPU_LEGEND_HEADER_LENS);
             let intrinsic_widths = &(variable_intrinsic_results.0)[0..variable_intrinsic_results.1];
 
-            let (border_and_title_style, highlight_style) = if is_on_widget {
-                (
-                    self.colours.highlighted_border_style,
-                    self.colours.currently_selected_text_style,
-                )
+            // Note we don't set highlight_style, as it should always be shown for this widget.
+            let border_and_title_style = if is_on_widget {
+                self.colours.highlighted_border_style
             } else {
-                (self.colours.border_style, self.colours.text_style)
+                self.colours.border_style
             };
 
             // Draw
@@ -367,7 +365,7 @@ impl CpuGraphWidget for Painter {
                             .border_style(border_and_title_style),
                     )
                     .header_style(self.colours.table_header_style)
-                    .highlight_style(highlight_style)
+                    .highlight_style(self.colours.currently_selected_text_style)
                     .widths(
                         &(intrinsic_widths
                             .iter()
diff --git a/src/canvas/widgets/process_table.rs b/src/canvas/widgets/process_table.rs
index 8d6ea0bb..cce7835c 100644
--- a/src/canvas/widgets/process_table.rs
+++ b/src/canvas/widgets/process_table.rs
@@ -36,7 +36,7 @@ pub trait ProcessTableWidget {
         widget_id: u64,
     );
 
-    /// Draws the process sort box.
+    /// Draws the process search field.
     /// - `widget_id` represents the widget ID of the search box itself --- NOT the process widget
     /// state that is stored.
     ///
@@ -173,15 +173,6 @@ impl ProcessTableWidget for Painter {
                 .finalized_process_data_map
                 .get(&widget_id)
             {
-                // Admittedly this is kinda a hack... but we need to:
-                // * Scroll
-                // * Show/hide elements based on scroll position
-                //
-                // As such, we use a process_counter to know when we've
-                // hit the process we've currently scrolled to.
-                // We also need to move the list - we can
-                // do so by hiding some elements!
-
                 let table_gap = if draw_loc.height < TABLE_GAP_HEIGHT_LIMIT {
                     0
                 } else {
@@ -217,39 +208,52 @@ impl ProcessTableWidget for Painter {
                 // Draw!
                 let is_proc_widget_grouped = proc_widget_state.is_grouped;
                 let is_using_command = proc_widget_state.is_using_command;
+                let is_tree = proc_widget_state.is_tree_mode;
                 let mem_enabled = proc_widget_state.columns.is_enabled(&ProcessSorting::Mem);
+
+                // FIXME: [PROC OPTIMIZE] This can definitely be optimized; string references work fine here!
                 let process_rows = sliced_vec.iter().map(|process| {
-                    Row::Data(
-                        vec![
-                            if is_proc_widget_grouped {
-                                process.group_pids.len().to_string()
+                    let data = vec![
+                        if is_proc_widget_grouped {
+                            process.group_pids.len().to_string()
+                        } else {
+                            process.pid.to_string()
+                        },
+                        if is_tree {
+                            if let Some(prefix) = &process.process_description_prefix {
+                                prefix.clone()
                             } else {
-                                process.pid.to_string()
-                            },
-                            if is_using_command {
-                                process.command.clone()
-                            } else {
-                                process.name.clone()
-                            },
-                            format!("{:.1}%", process.cpu_percent_usage),
-                            if mem_enabled {
-                                format!("{:.0}{}", process.mem_usage_str.0, process.mem_usage_str.1)
-                            } else {
-                                format!("{:.1}%", process.mem_percent_usage)
-                            },
-                            process.read_per_sec.to_string(),
-                            process.write_per_sec.to_string(),
-                            process.total_read.to_string(),
-                            process.total_write.to_string(),
-                            process.process_state.to_string(),
-                        ]
-                        .into_iter(),
-                    )
+                                String::default()
+                            }
+                        } else if is_using_command {
+                            process.command.clone()
+                        } else {
+                            process.name.clone()
+                        },
+                        format!("{:.1}%", process.cpu_percent_usage),
+                        if mem_enabled {
+                            format!("{:.0}{}", process.mem_usage_str.0, process.mem_usage_str.1)
+                        } else {
+                            format!("{:.1}%", process.mem_percent_usage)
+                        },
+                        process.read_per_sec.clone(),
+                        process.write_per_sec.clone(),
+                        process.total_read.clone(),
+                        process.total_write.clone(),
+                        process.process_state.clone(),
+                    ]
+                    .into_iter();
+
+                    if process.is_disabled_entry {
+                        Row::StyledData(data, self.colours.disabled_text_style)
+                    } else {
+                        Row::Data(data)
+                    }
                 });
 
                 let process_headers = proc_widget_state.columns.get_column_headers(
                     &proc_widget_state.process_sorting_type,
-                    proc_widget_state.process_sorting_reverse,
+                    proc_widget_state.is_process_sort_descending,
                 );
 
                 let process_headers_lens: Vec<usize> = process_headers
@@ -269,6 +273,8 @@ impl ProcessTableWidget for Painter {
                     }
                 } else if proc_widget_state.is_using_command {
                     vec![0.05, 0.7, 0.05, 0.05, 0.03, 0.03, 0.03, 0.03]
+                } else if proc_widget_state.is_tree_mode {
+                    vec![0.05, 0.4, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1]
                 } else {
                     vec![0.1, 0.2, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1]
                 };
@@ -280,6 +286,7 @@ impl ProcessTableWidget for Painter {
                 let intrinsic_widths =
                     &(variable_intrinsic_results.0)[0..variable_intrinsic_results.1];
 
+                // TODO: gotop's "x out of y" thing is really nice to help keep track of the scroll position.
                 f.render_stateful_widget(
                     Table::new(process_headers.iter(), process_rows)
                         .block(process_block)
@@ -592,6 +599,7 @@ impl ProcessTableWidget for Painter {
                 .iter()
                 .map(|column| Row::Data(vec![column].into_iter()));
 
+            // FIXME: [State] Shorten state to small form if it can't fit...?
             let column_state = &mut proc_widget_state.columns.column_state;
             column_state.select(Some(
                 proc_widget_state
diff --git a/src/constants.rs b/src/constants.rs
index 5d58848c..99f663ce 100644
--- a/src/constants.rs
+++ b/src/constants.rs
@@ -92,7 +92,7 @@ pub const CPU_HELP_TEXT: [&str; 2] = [
 
 // TODO [Help]: Search in help?
 // TODO [Help]: Move to using tables for easier formatting?
-pub const PROCESS_HELP_TEXT: [&str; 12] = [
+pub const PROCESS_HELP_TEXT: [&str; 13] = [
     "3 - Process widget\n",
     "dd               Kill the selected process\n",
     "c                Sort by CPU usage, press again to reverse sorting order\n",
@@ -104,7 +104,8 @@ pub const PROCESS_HELP_TEXT: [&str; 12] = [
     "P                Toggle between showing the full command or just the process name\n",
     "s, F6            Open process sort widget\n",
     "I                Invert current sort\n",
-    "%                Toggle between values and percentages for memory usage",
+    "%                Toggle between values and percentages for memory usage\n",
+    "t, F5            Toggle tree mode",
 ];
 
 pub const SEARCH_HELP_TEXT: [&str; 46] = [
@@ -116,9 +117,9 @@ pub const SEARCH_HELP_TEXT: [&str; 46] = [
     "Ctrl-u           Clear the current search query\n",
     "Backspace        Delete the character behind the cursor\n",
     "Delete           Delete the character at the cursor\n",
-    "Alt-c/F1         Toggle matching case\n",
-    "Alt-w/F2         Toggle matching the entire word\n",
-    "Alt-r/F3         Toggle using regex\n",
+    "Alt-c, F1        Toggle matching case\n",
+    "Alt-w, F2        Toggle matching the entire word\n",
+    "Alt-r, F3        Toggle using regex\n",
     "Left, Alt-h      Move cursor left\n",
     "Right, Alt-l     Move cursor right\n",
     "\n",
@@ -142,8 +143,8 @@ pub const SEARCH_HELP_TEXT: [&str; 46] = [
     "<=               ex: cpu <= 1\n",
     "\n",
     "Logical operators:\n",
-    "and/&&/<Space>   ex: btm and cpu > 1 and mem > 1\n",
-    "or/||            ex: btm or firefox\n",
+    "and, &&, <Space> ex: btm and cpu > 1 and mem > 1\n",
+    "or, ||           ex: btm or firefox\n",
     "\n",
     "Supported units:\n",
     "B                ex: read > 1 b\n",
diff --git a/src/data_conversion.rs b/src/data_conversion.rs
index bf38483e..b7e3bb3a 100644
--- a/src/data_conversion.rs
+++ b/src/data_conversion.rs
@@ -1,12 +1,13 @@
 //! This mainly concerns converting collected data into things that the canvas
 //! can actually handle.
-
-use std::collections::HashMap;
-
+use crate::Pid;
 use crate::{
     app::{data_farmer, data_harvester, App, Filter},
-    utils::gen_util::*,
+    utils::{self, gen_util::*},
 };
+use data_harvester::processes::ProcessSorting;
+use indexmap::IndexSet;
+use std::collections::{HashMap, VecDeque};
 
 /// Point is of time, data
 type Point = (f64, f64);
@@ -38,16 +39,19 @@ pub struct ConvertedNetworkData {
     // mean_tx: f64,
 }
 
+// TODO: [REFACTOR] Process data... stuff really needs a rewrite.  Again.
 #[derive(Clone, Default, Debug)]
 pub struct ConvertedProcessData {
-    pub pid: u32,
+    pub pid: Pid,
+    pub ppid: Option<Pid>,
     pub name: String,
     pub command: String,
+    pub is_thread: Option<bool>,
     pub cpu_percent_usage: f64,
     pub mem_percent_usage: f64,
     pub mem_usage_bytes: u64,
     pub mem_usage_str: (f64, String),
-    pub group_pids: Vec<u32>,
+    pub group_pids: Vec<Pid>,
     pub read_per_sec: String,
     pub write_per_sec: String,
     pub total_read: String,
@@ -57,20 +61,11 @@ pub struct ConvertedProcessData {
     pub tr_f64: f64,
     pub tw_f64: f64,
     pub process_state: String,
-}
-
-#[derive(Clone, Default, Debug)]
-pub struct SingleProcessData {
-    pub pid: u32,
-    pub cpu_percent_usage: f64,
-    pub mem_percent_usage: f64,
-    pub mem_usage_bytes: u64,
-    pub group_pids: Vec<u32>,
-    pub read_per_sec: u64,
-    pub write_per_sec: u64,
-    pub total_read: u64,
-    pub total_write: u64,
-    pub process_state: String,
+    pub process_char: char,
+    /// Prefix printed before the process when displayed.
+    pub process_description_prefix: Option<String>,
+    /// Whether to mark this process entry as disabled (mostly for tree mode).
+    pub is_disabled_entry: bool,
 }
 
 #[derive(Clone, Default, Debug)]
@@ -418,6 +413,9 @@ pub enum ProcessNamingType {
 pub fn convert_process_data(
     current_data: &data_farmer::DataCollection,
 ) -> Vec<ConvertedProcessData> {
+    // FIXME: Thread highlighting and hiding support
+    // For macOS see https://github.com/hishamhm/htop/pull/848/files
+
     current_data
         .process_harvest
         .iter()
@@ -437,6 +435,8 @@ pub fn convert_process_data(
 
             ConvertedProcessData {
                 pid: process.pid,
+                ppid: process.parent_pid,
+                is_thread: None,
                 name: process.name.to_string(),
                 command: process.command.to_string(),
                 cpu_percent_usage: process.cpu_usage_percent,
@@ -453,21 +453,379 @@ pub fn convert_process_data(
                 tr_f64: process.total_read_bytes as f64,
                 tw_f64: process.total_write_bytes as f64,
                 process_state: process.process_state.to_owned(),
+                process_char: process.process_state_char,
+                process_description_prefix: None,
+                is_disabled_entry: false,
             }
         })
         .collect::<Vec<_>>()
 }
 
-pub fn group_process_data(
-    single_process_data: &[ConvertedProcessData], is_using_command: ProcessNamingType,
+const BRANCH_ENDING: char = '└';
+const BRANCH_VERTICAL: char = '│';
+const BRANCH_SPLIT: char = '├';
+const BRANCH_HORIZONTAL: char = '─';
+
+pub fn tree_process_data(
+    single_process_data: &[ConvertedProcessData], is_using_command: bool,
+    sort_type: &ProcessSorting, is_sort_descending: bool,
 ) -> Vec<ConvertedProcessData> {
+    // TODO: [TREE] Allow for collapsing entries.
+
+    // Let's first build up a (really terrible) parent -> child mapping...
+    // At the same time, let's make a mapping of PID -> process data!
+    let mut parent_child_mapping: HashMap<Pid, IndexSet<Pid>> = HashMap::default();
+    let mut pid_process_mapping: HashMap<Pid, &ConvertedProcessData> = HashMap::default();
+    let mut orphan_set: IndexSet<Pid> = IndexSet::new();
+
+    single_process_data.iter().for_each(|process| {
+        if let Some(ppid) = process.ppid {
+            orphan_set.insert(ppid);
+        }
+        orphan_set.insert(process.pid);
+    });
+
+    single_process_data.iter().for_each(|process| {
+        // Create a mapping for the process if it DNE.
+        parent_child_mapping
+            .entry(process.pid)
+            .or_insert_with(IndexSet::new);
+        pid_process_mapping.insert(process.pid, process);
+
+        // Insert its mapping to the process' parent if needed (create if it DNE).
+        if let Some(ppid) = process.ppid {
+            orphan_set.remove(&process.pid);
+            parent_child_mapping
+                .entry(ppid)
+                .or_insert_with(IndexSet::new)
+                .insert(process.pid);
+        }
+    });
+
+    // Keep only orphans, or promote children of orphans to a top-level orphan
+    // if their parents DNE in our pid to process mapping...
+    #[allow(clippy::redundant_clone)]
+    orphan_set.clone().iter().for_each(|pid| {
+        if pid_process_mapping.get(pid).is_none() {
+            // DNE!  Promote the mapped children and remove the current parent...
+            orphan_set.remove(pid);
+            if let Some(children) = parent_child_mapping.get(pid) {
+                orphan_set.extend(children);
+            }
+        }
+    });
+
+    // Turn the parent-child mapping into a "list" via DFS...
+    let mut pids_to_explore: VecDeque<Pid> = orphan_set.into_iter().collect();
+    let mut explored_pids: Vec<Pid> = vec![];
+    let mut lines: Vec<String> = vec![];
+
+    /// A post-order traversal to correctly prune entire branches that only contain children
+    /// that are disabled and themselves are also disabled ~~wait that sounds wrong~~.
+    ///
+    /// Basically, go through the hashmap, and prune out all branches that are no longer relevant.
+    fn prune_disabled_pids(
+        current_pid: Pid, parent_child_mapping: &mut HashMap<Pid, IndexSet<Pid>>,
+        pid_process_mapping: &HashMap<Pid, &ConvertedProcessData>,
+    ) -> bool {
+        // Let's explore all the children first, and make sure they (and their children)
+        // aren't all disabled...
+        let mut are_all_children_disabled = true;
+        if let Some(children) = parent_child_mapping.get(&current_pid) {
+            for child_pid in children.clone() {
+                let is_child_disabled =
+                    prune_disabled_pids(child_pid, parent_child_mapping, pid_process_mapping);
+
+                if is_child_disabled {
+                    if let Some(current_mapping) = parent_child_mapping.get_mut(&current_pid) {
+                        current_mapping.remove(&child_pid);
+                    }
+                } else if are_all_children_disabled {
+                    are_all_children_disabled = false;
+                }
+            }
+        }
+
+        // Now consider the current pid and whether to prune...
+        // If the node itself is not disabled, then never prune.  If it is, then check if all
+        // of its are disabled.
+        if let Some(process) = pid_process_mapping.get(&current_pid) {
+            if process.is_disabled_entry && are_all_children_disabled {
+                parent_child_mapping.remove(&current_pid);
+                return true;
+            }
+        }
+
+        false
+    }
+
+    fn sort_remaining_pids(
+        current_pid: Pid, sort_type: &ProcessSorting, is_sort_descending: bool,
+        parent_child_mapping: &mut HashMap<Pid, IndexSet<Pid>>,
+        pid_process_mapping: &HashMap<Pid, &ConvertedProcessData>,
+    ) {
+        // Sorting is special for tree data.  So, by default, things are "sorted"
+        // via the DFS, except for (at least Unix) PID 1 and 2, which are in that order.
+        // Otherwise, since this is DFS of the scanned PIDs (which are in order), you actually
+        // get a REVERSE order --- so, you get higher PIDs earlier than lower ones.
+        // But this is a tree.  So, you'll get a bit of a combination, but the general idea
+        // is that in a tree level, it's descending order, except, again, for the first layer.
+        // This is how htop does it by default.
+        //
+        // So how do we "sort"?  The current idea is that:
+        // - We sort *per-level*.  Say, I want to sort by CPU.  The "first level" is sorted
+        //   by CPU in terms of its usage.  All its direct children are sorted by CPU
+        //   with *their* siblings.  Etc.
+        // - The default is thus PIDs in reverse order (descending).  We set it to this when
+        //   we first enable the mode.
+
+        // So first, let's look at the children... (post-order again)
+        if let Some(children) = parent_child_mapping.get(&current_pid) {
+            let mut to_sort_vec: Vec<(Pid, &ConvertedProcessData)> = vec![];
+            for child_pid in children.clone() {
+                if let Some(child_process) = pid_process_mapping.get(&child_pid) {
+                    to_sort_vec.push((child_pid, child_process));
+                }
+                sort_remaining_pids(
+                    child_pid,
+                    sort_type,
+                    is_sort_descending,
+                    parent_child_mapping,
+                    pid_process_mapping,
+                );
+            }
+
+            // Now let's sort the immediate children!
+            sort_vec(&mut to_sort_vec, sort_type, is_sort_descending);
+
+            // Need to reverse what we got, apparently...
+            if let Some(current_mapping) = parent_child_mapping.get_mut(&current_pid) {
+                *current_mapping = to_sort_vec
+                    .iter()
+                    .rev()
+                    .map(|(pid, _proc)| *pid)
+                    .collect::<IndexSet<Pid>>();
+            }
+        }
+    }
+
+    fn sort_vec(
+        to_sort_vec: &mut Vec<(Pid, &ConvertedProcessData)>, sort_type: &ProcessSorting,
+        is_sort_descending: bool,
+    ) {
+        // Sort by PID first (descending)
+        to_sort_vec.sort_by(|a, b| utils::gen_util::get_ordering(a.1.pid, b.1.pid, false));
+
+        match sort_type {
+            ProcessSorting::CpuPercent => {
+                to_sort_vec.sort_by(|a, b| {
+                    utils::gen_util::get_ordering(
+                        a.1.cpu_percent_usage,
+                        b.1.cpu_percent_usage,
+                        is_sort_descending,
+                    )
+                });
+            }
+            ProcessSorting::Mem => {
+                to_sort_vec.sort_by(|a, b| {
+                    utils::gen_util::get_ordering(
+                        a.1.mem_usage_bytes,
+                        b.1.mem_usage_bytes,
+                        is_sort_descending,
+                    )
+                });
+            }
+            ProcessSorting::MemPercent => {
+                to_sort_vec.sort_by(|a, b| {
+                    utils::gen_util::get_ordering(
+                        a.1.mem_percent_usage,
+                        b.1.mem_percent_usage,
+                        is_sort_descending,
+                    )
+                });
+            }
+            ProcessSorting::ProcessName => {
+                to_sort_vec.sort_by(|a, b| {
+                    utils::gen_util::get_ordering(
+                        &a.1.name.to_lowercase(),
+                        &b.1.name.to_lowercase(),
+                        is_sort_descending,
+                    )
+                });
+            }
+            ProcessSorting::Command => to_sort_vec.sort_by(|a, b| {
+                utils::gen_util::get_ordering(
+                    &a.1.command.to_lowercase(),
+                    &b.1.command.to_lowercase(),
+                    is_sort_descending,
+                )
+            }),
+            ProcessSorting::Pid => {
+                if is_sort_descending {
+                    to_sort_vec.sort_by(|a, b| {
+                        utils::gen_util::get_ordering(a.0, b.0, is_sort_descending)
+                    });
+                }
+            }
+            ProcessSorting::ReadPerSecond => {
+                to_sort_vec.sort_by(|a, b| {
+                    utils::gen_util::get_ordering(a.1.rps_f64, b.1.rps_f64, is_sort_descending)
+                });
+            }
+            ProcessSorting::WritePerSecond => {
+                to_sort_vec.sort_by(|a, b| {
+                    utils::gen_util::get_ordering(a.1.wps_f64, b.1.wps_f64, is_sort_descending)
+                });
+            }
+            ProcessSorting::TotalRead => {
+                to_sort_vec.sort_by(|a, b| {
+                    utils::gen_util::get_ordering(a.1.tr_f64, b.1.tr_f64, is_sort_descending)
+                });
+            }
+            ProcessSorting::TotalWrite => {
+                to_sort_vec.sort_by(|a, b| {
+                    utils::gen_util::get_ordering(a.1.tw_f64, b.1.tw_f64, is_sort_descending)
+                });
+            }
+            ProcessSorting::State => to_sort_vec.sort_by(|a, b| {
+                utils::gen_util::get_ordering(
+                    &a.1.process_state.to_lowercase(),
+                    &b.1.process_state.to_lowercase(),
+                    is_sort_descending,
+                )
+            }),
+            ProcessSorting::Count => {
+                // Should never occur in this case.
+            }
+        }
+    }
+
+    /// A DFS traversal to correctly build the prefix lines (the pretty '├' and '─' lines) and
+    /// the correct order to the PID tree as a vector (DFS is the default order htop seems to use
+    /// so we're shamelessly copying that).
+    fn build_explored_pids(
+        current_pid: Pid, parent_child_mapping: &HashMap<Pid, IndexSet<Pid>>,
+        prev_drawn_lines: &str,
+    ) -> (Vec<Pid>, Vec<String>) {
+        let mut explored_pids: Vec<Pid> = vec![current_pid];
+        let mut lines: Vec<String> = vec![];
+
+        if let Some(children) = parent_child_mapping.get(&current_pid) {
+            for (itx, child) in children.iter().rev().enumerate() {
+                let new_drawn_lines = if itx == children.len() - 1 {
+                    format!("{}   ", prev_drawn_lines)
+                } else {
+                    format!("{}{}  ", prev_drawn_lines, BRANCH_VERTICAL)
+                };
+
+                let (pid_res, branch_res) =
+                    build_explored_pids(*child, parent_child_mapping, new_drawn_lines.as_str());
+
+                if itx == children.len() - 1 {
+                    lines.push(format!(
+                        "{}{}",
+                        prev_drawn_lines,
+                        if !new_drawn_lines.is_empty() {
+                            format!("{}{} ", BRANCH_ENDING, BRANCH_HORIZONTAL)
+                        } else {
+                            String::default()
+                        }
+                    ));
+                } else {
+                    lines.push(format!(
+                        "{}{}",
+                        prev_drawn_lines,
+                        if !new_drawn_lines.is_empty() {
+                            format!("{}{} ", BRANCH_SPLIT, BRANCH_HORIZONTAL)
+                        } else {
+                            String::default()
+                        }
+                    ));
+                }
+
+                explored_pids.extend(pid_res);
+                lines.extend(branch_res);
+            }
+        }
+
+        (explored_pids, lines)
+    }
+
+    let mut to_sort_vec = Vec::new();
+    for pid in pids_to_explore {
+        if let Some(process) = pid_process_mapping.get(&pid) {
+            to_sort_vec.push((pid, *process));
+        }
+    }
+    sort_vec(&mut to_sort_vec, sort_type, is_sort_descending);
+    pids_to_explore = to_sort_vec.iter().map(|(pid, _proc)| *pid).collect();
+
+    while let Some(current_pid) = pids_to_explore.pop_front() {
+        if !prune_disabled_pids(current_pid, &mut parent_child_mapping, &pid_process_mapping) {
+            sort_remaining_pids(
+                current_pid,
+                sort_type,
+                is_sort_descending,
+                &mut parent_child_mapping,
+                &pid_process_mapping,
+            );
+
+            let (pid_res, branch_res) = build_explored_pids(current_pid, &parent_child_mapping, "");
+            lines.push(String::default());
+            lines.extend(branch_res);
+            explored_pids.extend(pid_res);
+        }
+    }
+
+    // Now let's "rearrange" our current list of converted process data into the correct
+    // order required... and we're done!
+    explored_pids
+        .iter()
+        .zip(lines)
+        .filter_map(|(pid, prefix)| match pid_process_mapping.remove(pid) {
+            Some(process) => {
+                let mut p = process.clone();
+                p.process_description_prefix = Some(format!(
+                    "{}{}",
+                    prefix,
+                    if is_using_command {
+                        &p.command
+                    } else {
+                        &p.name
+                    }
+                ));
+                Some(p)
+            }
+            None => None,
+        })
+        .collect::<Vec<_>>()
+}
+
+pub fn group_process_data(
+    single_process_data: &[ConvertedProcessData], is_using_command: bool,
+) -> Vec<ConvertedProcessData> {
+    #[derive(Clone, Default, Debug)]
+    struct SingleProcessData {
+        pub pid: Pid,
+        pub cpu_percent_usage: f64,
+        pub mem_percent_usage: f64,
+        pub mem_usage_bytes: u64,
+        pub group_pids: Vec<Pid>,
+        pub read_per_sec: f64,
+        pub write_per_sec: f64,
+        pub total_read: f64,
+        pub total_write: f64,
+        pub process_state: String,
+    }
+
     let mut grouped_hashmap: HashMap<String, SingleProcessData> = std::collections::HashMap::new();
 
     single_process_data.iter().for_each(|process| {
         let entry = grouped_hashmap
-            .entry(match is_using_command {
-                ProcessNamingType::Name => process.name.to_string(),
-                ProcessNamingType::Path => process.command.to_string(),
+            .entry(if is_using_command {
+                process.command.to_string()
+            } else {
+                process.name.to_string()
             })
             .or_insert(SingleProcessData {
                 pid: process.pid,
@@ -478,20 +836,20 @@ pub fn group_process_data(
         (*entry).mem_percent_usage += process.mem_percent_usage;
         (*entry).mem_usage_bytes += process.mem_usage_bytes;
         (*entry).group_pids.push(process.pid);
-        (*entry).read_per_sec += process.rps_f64 as u64;
-        (*entry).write_per_sec += process.wps_f64 as u64;
-        (*entry).total_read += process.tr_f64 as u64;
-        (*entry).total_write += process.tw_f64 as u64;
+        (*entry).read_per_sec += process.rps_f64;
+        (*entry).write_per_sec += process.wps_f64;
+        (*entry).total_read += process.tr_f64;
+        (*entry).total_write += process.tw_f64;
     });
 
     grouped_hashmap
         .iter()
         .map(|(identifier, process_details)| {
             let p = process_details.clone();
-            let converted_rps = get_exact_byte_values(p.read_per_sec, false);
-            let converted_wps = get_exact_byte_values(p.write_per_sec, false);
-            let converted_total_read = get_exact_byte_values(p.total_read, false);
-            let converted_total_write = get_exact_byte_values(p.total_write, false);
+            let converted_rps = get_exact_byte_values(p.read_per_sec as u64, false);
+            let converted_wps = get_exact_byte_values(p.write_per_sec as u64, false);
+            let converted_total_read = get_exact_byte_values(p.total_read as u64, false);
+            let converted_total_write = get_exact_byte_values(p.total_write as u64, false);
 
             let read_per_sec = format!("{:.*}{}/s", 0, converted_rps.0, converted_rps.1);
             let write_per_sec = format!("{:.*}{}/s", 0, converted_wps.0, converted_wps.1);
@@ -503,6 +861,8 @@ pub fn group_process_data(
 
             ConvertedProcessData {
                 pid: p.pid,
+                ppid: None,
+                is_thread: None,
                 name: identifier.to_string(),
                 command: identifier.to_string(),
                 cpu_percent_usage: p.cpu_percent_usage,
@@ -514,11 +874,14 @@ pub fn group_process_data(
                 write_per_sec,
                 total_read,
                 total_write,
-                rps_f64: p.read_per_sec as f64,
-                wps_f64: p.write_per_sec as f64,
-                tr_f64: p.total_read as f64,
-                tw_f64: p.total_write as f64,
-                process_state: p.process_state,
+                rps_f64: p.read_per_sec,
+                wps_f64: p.write_per_sec,
+                tr_f64: p.total_read,
+                tw_f64: p.total_write,
+                process_state: p.process_state, // TODO: What the heck
+                process_description_prefix: None,
+                process_char: char::default(), // TODO: What the heck
+                is_disabled_entry: false,
             }
         })
         .collect::<Vec<_>>()
diff --git a/src/lib.rs b/src/lib.rs
index 2c15c73d..ee6f2cfc 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -47,6 +47,12 @@ pub mod options;
 
 pub mod clap;
 
+#[cfg(target_family = "windows")]
+pub type Pid = usize;
+
+#[cfg(target_family = "unix")]
+pub type Pid = libc::pid_t;
+
 pub enum BottomEvent<I, J> {
     KeyInput(I),
     MouseInput(J),
@@ -111,6 +117,7 @@ pub fn handle_key_event_or_break(
             KeyCode::F(1) => app.toggle_ignore_case(),
             KeyCode::F(2) => app.toggle_search_whole_word(),
             KeyCode::F(3) => app.toggle_search_regex(),
+            KeyCode::F(5) => app.toggle_tree_mode(),
             KeyCode::F(6) => app.toggle_sort(),
             _ => {}
         }
@@ -458,88 +465,109 @@ pub fn update_all_process_lists(app: &mut App) {
     }
 }
 
-pub fn update_final_process_list(app: &mut App, widget_id: u64) {
-    let (is_invalid_or_blank, is_using_command) = match app.proc_state.widget_states.get(&widget_id)
-    {
-        Some(process_state) => (
+fn update_final_process_list(app: &mut App, widget_id: u64) {
+    let process_states = match app.proc_state.widget_states.get(&widget_id) {
+        Some(process_state) => Some((
             process_state
                 .process_search_state
                 .search_state
                 .is_invalid_or_blank_search(),
             process_state.is_using_command,
-        ),
-        None => (false, false),
+            process_state.is_grouped,
+            process_state.is_tree_mode,
+        )),
+        None => None,
     };
-    let is_grouped = app.is_grouped(widget_id);
 
-    if !app.is_frozen {
-        app.canvas_data.single_process_data = convert_process_data(&app.data_collection);
-    }
-
-    if is_grouped {
-        app.canvas_data.process_data = group_process_data(
-            &app.canvas_data.single_process_data,
-            if is_using_command {
-                ProcessNamingType::Path
-            } else {
-                ProcessNamingType::Name
-            },
-        );
-    } else {
-        app.canvas_data.process_data = app.canvas_data.single_process_data.clone();
-    }
-
-    let process_filter = app.get_process_filter(widget_id);
-    let filtered_process_data: Vec<ConvertedProcessData> = app
-        .canvas_data
-        .process_data
-        .iter()
-        .filter(|process| {
-            if !is_invalid_or_blank {
-                if let Some(process_filter) = process_filter {
-                    process_filter.check(&process, is_using_command)
-                } else {
-                    true
-                }
-            } else {
-                true
-            }
-        })
-        .cloned()
-        .collect::<Vec<_>>();
-
-    // Quick fix for tab updating the table headers
-    if let Some(proc_widget_state) = app.proc_state.get_mut_widget_state(widget_id) {
-        let mut resulting_processes = filtered_process_data;
-        sort_process_data(&mut resulting_processes, proc_widget_state);
-
-        if proc_widget_state.scroll_state.current_scroll_position >= resulting_processes.len() {
-            proc_widget_state.scroll_state.current_scroll_position =
-                resulting_processes.len().saturating_sub(1);
-            proc_widget_state.scroll_state.previous_scroll_position = 0;
-            proc_widget_state.scroll_state.scroll_direction = app::ScrollDirection::Down;
+    if let Some((is_invalid_or_blank, is_using_command, is_grouped, is_tree)) = process_states {
+        if !app.is_frozen {
+            app.canvas_data.single_process_data = convert_process_data(&app.data_collection);
         }
 
-        app.canvas_data
-            .finalized_process_data_map
-            .insert(widget_id, resulting_processes);
+        let process_filter = app.get_process_filter(widget_id);
+        let filtered_process_data: Vec<ConvertedProcessData> = if is_tree {
+            app.canvas_data
+                .single_process_data
+                .iter()
+                .map(|process| {
+                    let mut process_clone = process.clone();
+                    if !is_invalid_or_blank {
+                        if let Some(process_filter) = process_filter {
+                            process_clone.is_disabled_entry =
+                                !process_filter.check(&process_clone, is_using_command);
+                        }
+                    }
+                    process_clone
+                })
+                .collect::<Vec<_>>()
+        } else {
+            app.canvas_data
+                .single_process_data
+                .iter()
+                .filter(|process| {
+                    if !is_invalid_or_blank {
+                        if let Some(process_filter) = process_filter {
+                            process_filter.check(&process, is_using_command)
+                        } else {
+                            true
+                        }
+                    } else {
+                        true
+                    }
+                })
+                .cloned()
+                .collect::<Vec<_>>()
+        };
+
+        if let Some(proc_widget_state) = app.proc_state.get_mut_widget_state(widget_id) {
+            let mut finalized_process_data = if is_tree {
+                tree_process_data(
+                    &filtered_process_data,
+                    is_using_command,
+                    &proc_widget_state.process_sorting_type,
+                    proc_widget_state.is_process_sort_descending,
+                )
+            } else if is_grouped {
+                group_process_data(&filtered_process_data, is_using_command)
+            } else {
+                filtered_process_data
+            };
+
+            // Note tree mode is sorted well before this, as it's special.
+            if !is_tree {
+                sort_process_data(&mut finalized_process_data, proc_widget_state);
+            }
+
+            if proc_widget_state.scroll_state.current_scroll_position
+                >= finalized_process_data.len()
+            {
+                proc_widget_state.scroll_state.current_scroll_position =
+                    finalized_process_data.len().saturating_sub(1);
+                proc_widget_state.scroll_state.previous_scroll_position = 0;
+                proc_widget_state.scroll_state.scroll_direction = app::ScrollDirection::Down;
+            }
+
+            app.canvas_data
+                .finalized_process_data_map
+                .insert(widget_id, finalized_process_data);
+        }
     }
 }
 
-pub fn sort_process_data(
+fn sort_process_data(
     to_sort_vec: &mut Vec<ConvertedProcessData>, proc_widget_state: &app::ProcWidgetState,
 ) {
     to_sort_vec.sort_by(|a, b| {
         utils::gen_util::get_ordering(&a.name.to_lowercase(), &b.name.to_lowercase(), false)
     });
 
-    match proc_widget_state.process_sorting_type {
+    match &proc_widget_state.process_sorting_type {
         ProcessSorting::CpuPercent => {
             to_sort_vec.sort_by(|a, b| {
                 utils::gen_util::get_ordering(
                     a.cpu_percent_usage,
                     b.cpu_percent_usage,
-                    proc_widget_state.process_sorting_reverse,
+                    proc_widget_state.is_process_sort_descending,
                 )
             });
         }
@@ -548,7 +576,7 @@ pub fn sort_process_data(
                 utils::gen_util::get_ordering(
                     a.mem_usage_bytes,
                     b.mem_usage_bytes,
-                    proc_widget_state.process_sorting_reverse,
+                    proc_widget_state.is_process_sort_descending,
                 )
             });
         }
@@ -557,18 +585,18 @@ pub fn sort_process_data(
                 utils::gen_util::get_ordering(
                     a.mem_percent_usage,
                     b.mem_percent_usage,
-                    proc_widget_state.process_sorting_reverse,
+                    proc_widget_state.is_process_sort_descending,
                 )
             });
         }
         ProcessSorting::ProcessName => {
             // Don't repeat if false... it sorts by name by default anyways.
-            if proc_widget_state.process_sorting_reverse {
+            if proc_widget_state.is_process_sort_descending {
                 to_sort_vec.sort_by(|a, b| {
                     utils::gen_util::get_ordering(
                         &a.name.to_lowercase(),
                         &b.name.to_lowercase(),
-                        proc_widget_state.process_sorting_reverse,
+                        proc_widget_state.is_process_sort_descending,
                     )
                 })
             }
@@ -577,7 +605,7 @@ pub fn sort_process_data(
             utils::gen_util::get_ordering(
                 &a.command.to_lowercase(),
                 &b.command.to_lowercase(),
-                proc_widget_state.process_sorting_reverse,
+                proc_widget_state.is_process_sort_descending,
             )
         }),
         ProcessSorting::Pid => {
@@ -586,7 +614,7 @@ pub fn sort_process_data(
                     utils::gen_util::get_ordering(
                         a.pid,
                         b.pid,
-                        proc_widget_state.process_sorting_reverse,
+                        proc_widget_state.is_process_sort_descending,
                     )
                 });
             }
@@ -596,7 +624,7 @@ pub fn sort_process_data(
                 utils::gen_util::get_ordering(
                     a.rps_f64,
                     b.rps_f64,
-                    proc_widget_state.process_sorting_reverse,
+                    proc_widget_state.is_process_sort_descending,
                 )
             });
         }
@@ -605,7 +633,7 @@ pub fn sort_process_data(
                 utils::gen_util::get_ordering(
                     a.wps_f64,
                     b.wps_f64,
-                    proc_widget_state.process_sorting_reverse,
+                    proc_widget_state.is_process_sort_descending,
                 )
             });
         }
@@ -614,7 +642,7 @@ pub fn sort_process_data(
                 utils::gen_util::get_ordering(
                     a.tr_f64,
                     b.tr_f64,
-                    proc_widget_state.process_sorting_reverse,
+                    proc_widget_state.is_process_sort_descending,
                 )
             });
         }
@@ -623,7 +651,7 @@ pub fn sort_process_data(
                 utils::gen_util::get_ordering(
                     a.tw_f64,
                     b.tw_f64,
-                    proc_widget_state.process_sorting_reverse,
+                    proc_widget_state.is_process_sort_descending,
                 )
             });
         }
@@ -631,7 +659,7 @@ pub fn sort_process_data(
             utils::gen_util::get_ordering(
                 &a.process_state.to_lowercase(),
                 &b.process_state.to_lowercase(),
-                proc_widget_state.process_sorting_reverse,
+                proc_widget_state.is_process_sort_descending,
             )
         }),
         ProcessSorting::Count => {
@@ -640,7 +668,7 @@ pub fn sort_process_data(
                     utils::gen_util::get_ordering(
                         a.group_pids.len(),
                         b.group_pids.len(),
-                        proc_widget_state.process_sorting_reverse,
+                        proc_widget_state.is_process_sort_descending,
                     )
                 });
             }
diff --git a/src/utils/gen_util.rs b/src/utils/gen_util.rs
index 3c97a2bd..2e13968f 100644
--- a/src/utils/gen_util.rs
+++ b/src/utils/gen_util.rs
@@ -91,19 +91,19 @@ pub fn get_simple_byte_values(bytes: u64, spacing: bool) -> (f64, String) {
 
 /// Gotta get partial ordering?  No problem, here's something to deal with it~
 pub fn get_ordering<T: std::cmp::PartialOrd>(
-    a_val: T, b_val: T, reverse_order: bool,
+    a_val: T, b_val: T, descending_order: bool,
 ) -> std::cmp::Ordering {
     match a_val.partial_cmp(&b_val) {
         Some(x) => match x {
             Ordering::Greater => {
-                if reverse_order {
+                if descending_order {
                     std::cmp::Ordering::Less
                 } else {
                     std::cmp::Ordering::Greater
                 }
             }
             Ordering::Less => {
-                if reverse_order {
+                if descending_order {
                     std::cmp::Ordering::Greater
                 } else {
                     std::cmp::Ordering::Less