This example shows a hierarchical tree of world countries, grouped first by continent and then by subregion. The visualization uses a horizontal tree layout with curved links to connect parent nodes to their children. It labels each node with its name, with font size decreasing at deeper levels. The diagram is created with d3.tree and d3.hierarchy, rendered as SVG paths and text elements, with zooming enabled through d3.zoom. The data comes from a static JSON file.