This interactive tree diagram displays hierarchical data with expandable and collapsible nodes. Clicking a node toggles its children, animating the layout transitions. The example is built with React and D3.js, using the `d3.layout.tree` API and `d3.svg.diagonal` projections to draw curved links. The SVG rendering includes a 750ms transition animation for nodes and links as the tree structure changes. Custom data defines family relationships, with nodes styled as white circles with steelblue strokes.