This example shows an interactive tree diagram of hospital departments, with nodes labeled by location or clinic name (e.g., KFSH, Riyad, Dental). Clicking a node collapses or expands its children with a smooth animated transition. The visualization uses D3 v3’s `d3.layout.tree` to compute node positions and `d3.svg.diagonal` for curved link paths. Data is loaded from an external JSON file, and SVG elements are updated via D3’s enter/update/exit pattern with a 1100-millisecond duration.