This example displays a population bar chart with overlaid genomic features, using D3 and React to visualize data from CSV files. It shows a set of bars representing population sizes on a linear scale, alongside four semi-transparent rectangles that highlight specific chromosomal regions. The visualization leverages D3's `scaleBand` and `scaleLinear` to map data to SVG coordinates, with gridlines and tick labels formatted using `d3.format`. React manages the asynchronous loading of both datasets via custom hooks, while the final SVG output is rendered through ReactDOM.