This visualization displays population over time by region, with multiple colored lines representing different world regions from 1950 to 2100. The chart uses D3 v5’s `nest()` to group data by region, `scaleTime` and `scaleLinear` for axes, and `line` with `curveBasis` to generate smooth paths. Data comes from UN population estimates and medium variant projections, processed by melting wide-format CSV data into tidy long format. A custom `colorLegend` function renders the categorical color scale, and the visualization includes gridlines, axis labels, and a title.