A treemap visualization displays the hierarchical structure of the flare.json dataset, with nested rectangles sized by either node size or leaf count. The interactive chart allows toggling between these two aggregation modes via radio buttons, triggering a smooth animated transition. Built with D3 v4, the visualization uses `d3.treemap`, `d3.hierarchy`, and `d3.scaleOrdinal` for coloring, rendering SVG cells with clipped text labels and tooltips.