diff --git a/src/lib.rs b/src/lib.rs
index f80e21b..a4d74e1 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,78 +1,12 @@
 //! Cyborg is a high-performance, modern, experimental rendering engine written
 //! in Rust.
 
-use std::collections::HashMap;
 use std::sync::{Arc, RwLock};
 use strum::IntoEnumIterator;
 
-#[derive(Copy, Clone, Debug, Hash, Eq, Ord, PartialEq, PartialOrd, strum::EnumIter)]
-pub enum PrePhase {}
+pub mod phase;
 
-#[derive(Copy, Clone, Debug, Hash, Eq, Ord, PartialEq, PartialOrd, strum::EnumIter)]
-pub enum ViewportPhase {}
-
-#[derive(Debug, Default)]
-pub struct PhaseList {
-    pub pre: Vec<PrePhase>,
-    pub viewport: Vec<ViewportPhase>,
-}
-
-impl PhaseList {
-    pub fn clear(&mut self) {
-        self.pre.clear();
-        self.viewport.clear();
-    }
-}
-
-#[derive(Debug, Default)]
-pub struct PhaseMultiMap<T> {
-    pub pre: HashMap<PrePhase, Vec<T>>,
-    pub viewport: HashMap<ViewportPhase, Vec<T>>,
-}
-
-impl<T: Copy + PartialEq> PhaseMultiMap<T> {
-    pub fn insert_multi(&mut self, keys: &PhaseList, val: T) {
-        for pre in keys.pre.iter() {
-            Self::insert(&mut self.pre, pre, val);
-        }
-
-        for viewport in keys.viewport.iter() {
-            Self::insert(&mut self.viewport, viewport, val);
-        }
-    }
-
-    pub fn iter_pre<'a>(&'a self, phase: &'a PrePhase) -> std::slice::Iter<'a, T> {
-        Self::iter(&self.pre, phase)
-    }
-
-    pub fn iter_viewport<'a>(&'a self, phase: &'a ViewportPhase) -> std::slice::Iter<'a, T> {
-        Self::iter(&self.viewport, phase)
-    }
-
-    fn insert<K>(map: &mut HashMap<K, Vec<T>>, key: &K, val: T)
-    where
-        K: std::hash::Hash + Eq + Copy,
-    {
-        if let Some(existing) = map.get_mut(key) {
-            if !existing.contains(&val) {
-                existing.push(val);
-            }
-        } else {
-            map.insert(*key, vec![val]);
-        }
-    }
-
-    fn iter<'a, K>(map: &'a HashMap<K, Vec<T>>, key: &'a K) -> std::slice::Iter<'a, T>
-    where
-        K: std::hash::Hash + Eq + Copy,
-    {
-        if let Some(vals) = map.get(key) {
-            vals.iter()
-        } else {
-            [].iter()
-        }
-    }
-}
+use phase::*;
 
 pub struct ViewportData;
 
diff --git a/src/phase.rs b/src/phase.rs
new file mode 100644
index 0000000..a985194
--- /dev/null
+++ b/src/phase.rs
@@ -0,0 +1,98 @@
+//! Definitions and containers for rendering phase identifiers.
+//!
+//! Rendering phases are organized into different groups, which represent
+//! different kinds of external data becoming available as the frame progresses.
+//! For example, OpenXR encourages applications to acquire its viewport poses
+//! as late into the frame as possible, to maximize the accuracy of pose
+//! prediction in the time before the frame is presented.
+//!
+//! The definitions in this module are meant to be expanded upon over time, so
+//! the containers make heavy use of generics to abstract functionality across
+//! different groups of phases.
+
+use std::collections::HashMap;
+
+/// The rendering pre-phase group; before viewport acquisition.
+#[derive(Copy, Clone, Debug, Hash, Eq, Ord, PartialEq, PartialOrd, strum::EnumIter)]
+pub enum PrePhase {}
+
+/// The main viewport rendering phase group.
+#[derive(Copy, Clone, Debug, Hash, Eq, Ord, PartialEq, PartialOrd, strum::EnumIter)]
+pub enum ViewportPhase {}
+
+/// A container of phases of each group.
+///
+/// Can be used with the [PhaseMultiMap] container to insert a value into
+/// multiple phases at once.
+#[derive(Debug, Default)]
+pub struct PhaseList {
+    pre: Vec<PrePhase>,
+    viewport: Vec<ViewportPhase>,
+}
+
+impl PhaseList {
+    /// Clears the list, removing all phases.
+    pub fn clear(&mut self) {
+        self.pre.clear();
+        self.viewport.clear();
+    }
+}
+
+/// Maps phases of each group to sets of values.
+///
+/// Used by the frame scheduler to organize which phases execute which render
+/// passes.
+#[derive(Debug, Default)]
+pub struct PhaseMultiMap<T> {
+    pre: HashMap<PrePhase, Vec<T>>,
+    viewport: HashMap<ViewportPhase, Vec<T>>,
+}
+
+impl<T: Copy + PartialEq> PhaseMultiMap<T> {
+    /// Inserts a value into multiple phases at once, keyed with a [PhaseList].
+    pub fn insert_multi(&mut self, keys: &PhaseList, val: T) {
+        for pre in keys.pre.iter() {
+            Self::insert(&mut self.pre, pre, val);
+        }
+
+        for viewport in keys.viewport.iter() {
+            Self::insert(&mut self.viewport, viewport, val);
+        }
+    }
+
+    /// Iterates over all values matching a [PrePhase].
+    pub fn iter_pre<'a>(&'a self, phase: &'a PrePhase) -> std::slice::Iter<'a, T> {
+        Self::iter(&self.pre, phase)
+    }
+
+    /// Iterates over all values matching a [ViewportPhase].
+    pub fn iter_viewport<'a>(&'a self, phase: &'a ViewportPhase) -> std::slice::Iter<'a, T> {
+        Self::iter(&self.viewport, phase)
+    }
+
+    /// Generic helper function for inserting a single value into a phase group map.
+    fn insert<K>(map: &mut HashMap<K, Vec<T>>, key: &K, val: T)
+    where
+        K: std::hash::Hash + Eq + Copy,
+    {
+        if let Some(existing) = map.get_mut(key) {
+            if !existing.contains(&val) {
+                existing.push(val);
+            }
+        } else {
+            map.insert(*key, vec![val]);
+        }
+    }
+
+    /// Generic helper function that iterates over a group's phase, if available.
+    fn iter<'a, K>(map: &'a HashMap<K, Vec<T>>, key: &'a K) -> std::slice::Iter<'a, T>
+    where
+        K: std::hash::Hash + Eq + Copy,
+    {
+        if let Some(vals) = map.get(key) {
+            vals.iter()
+        } else {
+            [].iter()
+        }
+    }
+}