This example displays the top 10 most populous countries as horizontal bars using React and D3 v5. It loads UN World Population Prospects 2019 data via d3.csv, sorts by 2020 population, and renders SVG rectangles with d3.scaleBand, d3.scaleLinear, and d3.max. The component structure separates axis and mark rendering into reusable functions, with d3.ticks generating the bottom axis labels and scaleBand domains for the left axis.