A hierarchical treemap displays the flare dataset, showing nested file sizes and counts as colored, labeled rectangles. The visualization uses `d3.treemap` with the `d3.treemapResquarify` tile method, rendering SVG rectangles and text with mouse-over titles. Radio buttons switch between summing by file size and by node count, triggering a 750ms `transition` that animates rectangle positions and dimensions. D3 v4 and `d3.scaleOrdinal` with `d3.schemeCategory20` color the cells.