From the Old Bailey Online

Treemap with headers: Offences 1700-99, categories and sub-categories

"A treemap recursively subdivides area into rectangles; the area of any node in the tree corresponds to its value." This treemap has category labels in headers, making it easier to interpret than the first example but less elegant. Doesn't show sub-category labels till you zoom in.

(click on rectangles to zoom in/out)