This example shows a hierarchical tree visualization of vehicle categories—Land, Air, and Water—with their subcategories as leaf nodes. The code uses d3.hierarchy and d3.tree to compute the layout, then renders the structure as SVG circles and connecting lines, with colors indicating depth (red for root, green for categories, blue for leaves). Labels are added as SVG text elements, while React wraps the D3 logic in a useEffect hook. The accompanying React component in index.jsx only sets static text, demonstrating a minimal React-D3 integration pattern.