diff --git a/src/fem/mod.rs b/src/fem/mod.rs
index c18f01a..cc32569 100644
--- a/src/fem/mod.rs
+++ b/src/fem/mod.rs
@@ -29,9 +29,13 @@ use vtkio::{
 const ELEMENT_NUMBERING_OFFSET: usize = 1;
 const ELEMENT_TYPE: &str = "C3D8R";
 pub const NODE_NUMBERING_OFFSET: usize = 1;
+
+/// The number of nodes in a hexahedral finite element.
 pub const NUM_NODES_HEX: usize = 8;
 
+/// A vector of finite element block IDs.
 pub type Blocks = Vec<usize>;
+
 pub type VecConnectivity = Vec<Vec<usize>>;
 pub type Metrics = Array1<f64>;
 pub type Nodes = Vec<usize>;
diff --git a/src/lib.rs b/src/lib.rs
index 469adb8..d69d533 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -16,16 +16,23 @@ mod fem;
 mod tree;
 mod voxel;
 
-pub use fem::{Blocks, FiniteElements, HexahedralFiniteElements, Smoothing, NUM_NODES_HEX};
+pub use fem::{Blocks, FiniteElements, HexahedralFiniteElements, Smoothing};
 pub use tree::{Octree, Tree};
 pub use voxel::{VoxelData, Voxels};
 
 use flavio::{math::TensorRank1Vec, mechanics::Vector as VectorFlavio};
 
+/// The number of spatial dimensions.
 const NSD: usize = 3;
 
+/// An element-to-node connectivity.
 pub type Connectivity<const N: usize> = Vec<[usize; N]>;
+
+/// A three-dimensional coordinate.
 pub type Coordinate = VectorFlavio<1>;
-pub type Coordinates = TensorRank1Vec<3, 1>;
-pub type Points = TensorRank1Vec<3, 1>;
+
+/// A vector of three-dimensional coordinates.
+pub type Coordinates = TensorRank1Vec<NSD, 1>;
+
+/// A three-dimensional vector.
 pub type Vector = VectorFlavio<1>;
diff --git a/src/tree/mod.rs b/src/tree/mod.rs
index dfee2e5..78387ce 100644
--- a/src/tree/mod.rs
+++ b/src/tree/mod.rs
@@ -2,8 +2,8 @@
 use std::time::Instant;
 
 use super::{
-    fem::NODE_NUMBERING_OFFSET, Coordinate, Coordinates, HexahedralFiniteElements, Points, Vector,
-    VoxelData, Voxels, NUM_NODES_HEX,
+    fem::{NODE_NUMBERING_OFFSET, NUM_NODES_HEX},
+    Coordinate, Coordinates, HexahedralFiniteElements, Vector, VoxelData, Voxels,
 };
 use flavio::math::{Tensor, TensorArray};
 use ndarray::{s, Axis};
@@ -15,11 +15,14 @@ const NUM_OCTANTS: usize = 8;
 type Cells = [Cell; NUM_OCTANTS];
 type Faces = [Option<usize>; NUM_FACES];
 type Indices = [usize; NUM_OCTANTS];
+
+/// The octree type.
 pub type Octree = Vec<Cell>;
 
+/// Methods for trees such as quadtrees or octrees.
 pub trait Tree {
     fn balance(&mut self, strong: bool);
-    fn from_points(levels: &usize, points: &Points) -> Self;
+    fn from_points(levels: &usize, points: &Coordinates) -> Self;
     fn from_voxels(voxels: Voxels) -> Self;
     fn into_finite_elements(
         self,
@@ -47,7 +50,7 @@ pub struct Cell {
 }
 
 impl Cell {
-    fn contains(&self, points: &Points) -> bool {
+    fn contains(&self, points: &Coordinates) -> bool {
         for point in points.iter() {
             if &point[0] >= self.get_min_x()
                 && &point[0] <= self.get_max_x()
@@ -633,7 +636,7 @@ impl Tree for Octree {
             }
         }
     }
-    fn from_points(levels: &usize, points: &Points) -> Self {
+    fn from_points(levels: &usize, points: &Coordinates) -> Self {
         let x_vals: Vec<f64> = points.iter().map(|point| point[0]).collect();
         let y_vals: Vec<f64> = points.iter().map(|point| point[1]).collect();
         let z_vals: Vec<f64> = points.iter().map(|point| point[2]).collect();
diff --git a/src/voxel/mod.rs b/src/voxel/mod.rs
index 50a50a8..d8f680d 100644
--- a/src/voxel/mod.rs
+++ b/src/voxel/mod.rs
@@ -25,10 +25,12 @@ use tiff::{
 
 type InitialNodalCoordinates = Vec<Option<Coordinate>>;
 type Nel = [usize; NSD];
-pub type VoxelData = Array3<u8>;
 type VoxelDataFlattened = Vec<u8>;
 type VoxelDataSized<const N: usize> = Vec<[usize; N]>;
 
+/// The segmentation data corresponding to voxels.
+pub type VoxelData = Array3<u8>;
+
 /// The voxels type.
 pub struct Voxels {
     data: VoxelData,