This example renders a collapsible tree graph in SVG using D3.js v3, with each node representing a person in a nested JSON data structure. Colored rectangles distinguish node types, and links connect parent to child nodes. The tree layout dynamically recalculates its dimensions based on node depth and width, and supports zoom and drag navigation via `d3.behavior.zoom`. Clicking a node expands or collapses its children with a smooth 750-millisecond transition, while tooltips and drop shadows enhance interactivity.