diff --git a/src/grid/storage.rs b/src/grid/storage.rs
index 1f71b5b5..f59b01b7 100644
--- a/src/grid/storage.rs
+++ b/src/grid/storage.rs
@@ -20,6 +20,13 @@ pub struct Storage<T> {
     inner: Vec<T>,
     zero: usize,
     visible_lines: Line,
+
+    /// Total number of lines currently active in the terminal (scrollback + visible)
+    ///
+    /// Shrinking this length allows reducing the number of lines in the scrollback buffer without
+    /// having to truncate the raw `inner` buffer.
+    /// As long as `len` is bigger than `inner`, it is also possible to grow the scrollback buffer
+    /// without any additional insertions.
     #[serde(skip)]
     len: usize,
 }