This interactive tree diagram displays the hierarchical organization of world countries, grouped by continent and subregion, using a dataset from the UN (data.json). The visualization employs D3 v5’s `tree` layout and `hierarchy` function to compute node positions, with `linkHorizontal` drawing the connecting paths. Node labels are not rendered in this example; instead, a steelblue background rect is drawn, and the chart is sized to fill the viewport via `document.body.clientWidth/Height`. The underlying data is static JSON, while a separate CSV file provides population figures, though these are not currently linked or displayed.