This interactive treemap visualizes a hierarchical dataset with nested rectangles sized by a primary numeric measure and colored by a secondary metric. Users can hover over nodes to see tooltips with additional data, while clicking parent and grandparent rectangles zooms into deeper levels of the hierarchy. Built with D3 v4, the implementation uses `d3.hierarchy`, `d3.treemap`, and `d3.nest` to aggregate data, with SVG rendering and smooth transitions between zoom states. The hover effects and tooltip functionality are implemented with CSS and JavaScript event handlers.