diff --git a/src/types.jl b/src/types.jl
index 7cb51ff1065e96d5b18276c316a6e697d4299245..0f6d11260318b6ab61db42734a2717dfd3727bbb 100644
--- a/src/types.jl
+++ b/src/types.jl
@@ -29,6 +29,11 @@ struct Track
     t::Float64
 end
 
+"""
+
+A simple quaternion derived from a `FieldVector` of StaticArrays, no more, no less.
+
+"""
 struct Quaternion{T} <: FieldVector{4, T}
     q0::T
     qx::T