This tree map displays US steel scrap exports by partner country and commodity type, with each rectangle sized according to trade value. The visualization supports drill-down interaction by clicking on a country to reveal its commodity breakdown, plus a reset button to return to the top level. Built with D3 v7, it uses `d3.hierarchy` and `d3.treemap` to compute the layout, renders SVG rectangles with native tooltips via the `title` element, and animates resizing through `transition`. Data comes from an external CSV file containing country, commodity, and value columns.