This brushable scatterplot matrix displays the classic Iris flower dataset, showing how four sepal and petal measurements relate to three iris species. Each cell in the grid plots one measurement pair, with points colored red, yellow, or blue by species. Users can drag a brush across any cell to highlight corresponding data points across all other scatterplots, with brushed points remaining colored while unselected points turn gray. The visualization uses D3 version 3 APIs including `d3.svg.brush()` for the interactive brushing, `d3.scale.linear()` for axes, and coordinates rendered as SVG circles.