In this example, the Uize.Dom.Tree.getTreeFromPage static method of the Uize.Dom.Tree module is being used to build a tree data object respresenting the structure of the document, by analyzing the occurrence of different CSS classes for section headings at different depths of the document (in this case, the CSS classes level1Header, level2Header, and level3Header). A tree data object like this can be supplied to a tree menu widget, or can otherwise be used to build UI for navigating to different sections of the document (a contents tree, for example). A tree data object can also be generated from nested lists using the Uize.Dom.Tree.getTreeFromList method (see the Get Tree from List example).