This example shows population trends over time for world regions, with multiple lines plotted on a shared time axis and colored by region. The chart uses a legend to identify regions, with lines sorted by their final population value. It loads data from UN population estimates CSV files, processes it with a custom melt function, and renders using D3 v5 with SVG. Key APIs include d3.line, d3.scaleTime, d3.scaleLinear, d3.scaleOrdinal, d3.nest, and d3.axisBottom.