diff --git a/src/color/mod.rs b/src/color/mod.rs
index bdc8b93..1dd3c83 100644
--- a/src/color/mod.rs
+++ b/src/color/mod.rs
@@ -1,3 +1,19 @@
+//! A color is internally represented as either RGBA or HSLA.
+//! Colors can be constructed in SASS through names (e.g. red, blue, aqua)
+//! or the builtin functions `rgb()`, `rgba()`, `hsl()`, and `hsla()`,
+//! all of which can accept 1-4 arguments.
+//!
+//! It is necessary to retain the original values with which the
+//! color was constructed.
+//! E.g. `hsla(.999999999999, 100, 100, 1)` should retain its full
+//! values to an arbitrary precision.
+//!
+//! Named colors are created using RGB values
+//! E.g. `red` = `rgba(255, 0, 0, 1)`
+//!
+//! In addition, named colors retain their original casing,
+//! so `rEd` should be emitted as `rEd`.
+
 use std::convert::TryFrom;
 use std::fmt::{self, Display};
 
diff --git a/src/color/name.rs b/src/color/name.rs
index 2ee359d..484b13f 100644
--- a/src/color/name.rs
+++ b/src/color/name.rs
@@ -1,3 +1,6 @@
+//! A big dictionary of named colors and their
+//! corresponding RGBA values
+
 use std::convert::TryFrom;
 use std::fmt::{self, Display};
 
diff --git a/src/unit/conversion.rs b/src/unit/conversion.rs
index 186f6c9..9e3977d 100644
--- a/src/unit/conversion.rs
+++ b/src/unit/conversion.rs
@@ -1,3 +1,7 @@
+//! A big dictionary of units and their conversion ratios.
+//!
+//! Arbitrary precision is retained.
+
 use std::collections::HashMap;
 use std::f64::consts::PI;
 use std::string::ToString;