A treemap visualizes total COVID deaths per 10 million people across Sweden, Denmark, and Norway, using each country's latest recorded value from a CSV dataset. The treemap layout, sized at 800×500 pixels, is generated with `d3.treemap()` on a `d3.hierarchy` object. Each country appears as a colored rectangle, filled via `d3.countryColors`, with labels and hover tooltips. The example uses D3 v7 with SVG rendering, sorting records by date to select the most recent death rate per country.