This example visualizes the hierarchy of world countries using a tree diagram. The root node represents the World, branching into continents, subregions, and finally individual countries based on the data.json structure. The tree is rendered with D3.js v5, using the `d3.tree` layout, `d3.hierarchy`, and `d3.linkHorizontal` for the edges. The SVG is drawn with text labels and styled paths, and a `d3.zoom` component enables interactive pan and zoom.