A stacked horizontal bar chart displays the percentage distribution of four iris measurements—sepal length, sepal width, petal length, and petal width—across three species. Using d3.stack and d3.scaleBand, each species row segments colored rectangles proportionally, with a tooltip showing exact percentages on hover. The SVG renders with d3.axisBottom and d3.axisLeft, and the iris dataset is loaded from a CSV file.