This example shows a horizontal tree diagram of world regions and countries, using a hierarchical dataset that groups nations by continent and subregion. The code builds the layout with `d3.tree()` and `d3.hierarchy()`, then renders the parent-child connections as curved SVG paths via `d3.linkHorizontal()`. Each node represents a geographic entity, with the root labeled “World” and branches extending through continents like Asia. The visualization responds to the full browser viewport, with the SVG sized to the window dimensions.