A line chart displays population growth for world regions from 1950 to 2100, with each region colored via d3.scaleOrdinal and d3.schemeCategory10. Moving the mouse over the chart triggers d3.mouse to invert the x-scale, updating a vertical line marking the selected year. The visualization uses d3.csv to load UN population data, d3.nest to group by region, and d3.line with curveBasis to draw the paths.