The example HTML structure is an outer div that holds all of the panels. Then, each panel is just a couple of DIVs (one for the header and one for the content) wrapped in an outer DIV. You can actually use elements other than divs.

The height of the content and the panels is fixed to display inplace without effecting other page elements. The library is built off prototype/scriptaculous, but doesnt need them to run.

If a panel has too much content for the fixed height, it will display scrollbars.