This example shows a family tree rendered as an interactive hierarchical diagram using D3.js. The visualization displays a root node ("nikhil") with four children, each branching to two leaf nodes, demonstrating a simple three-level genealogy structure. The tree layout positions nodes vertically based on depth, with collapsible behavior triggered by clicking any node. The code uses D3’s `layout.tree()` and `svg.diagonal()` functions, with SVG elements styled via CSS, while animated transitions between states are handled by D3’s `.transition()` method over 750 milliseconds.