This example presents a three-layered hierarchical tree of programming languages, categorizing them into Compiled, Interpreted, and Scripting groups. Built with D3.js v7, it uses the `d3.stratify()` and `d3.tree()` layout APIs to position nodes, with `d3.linkVertical()` drawing the connecting paths. The SVG rendering colors circles by depth using `d3.scaleOrdinal()`, with labels for each language node. Data is defined inline in the HTML.