A ThemeRiver visualization displays changes in Massachusetts home sale prices over time, stacked into flowing streams by bedroom count. The chart uses D3 v6 to load CSV data, transforms it via the `d3.stack` generator, and renders smooth SVG areas with `d3.area` and `curveBasis`. Time and price scales map dates to the x-axis and cumulative price ranges to the y-axis, while each stream is colored by housing category.