This treemap visualizes the total export values of steel scrap commodities by partner country, using a hierarchical layout where each country is a top-level branch and individual commodities become leaf cells. The diagram is initially aggregated to country level, but users can click any country cell to drill down and reveal its commodity breakdown, with a reset button to return to the overview. Cell size encodes total trade value, while color runs from light to dark blue via a sequential scale based on the maximum leaf value. The visualization is built with D3 v7, using `d3.hierarchy` for tree construction, `d3.treemap` for layout, and SVG transitions with 500-millisecond durations to animate changes between drill-down levels. Tooltips on each cell display either the country total or the commodity name and value, and text labels are wrapped to fit within each cell’s dimensions. Data is loaded from a CSV file containing partnerCountry, commodityDescription, and Value columns, representing U.S. steel scrap exports.