This scatter plot matrix visualizes the Iris dataset, showing pairwise relationships between four flower measurements. The diagonal cells display histograms of each individual attribute, while off-diagonal cells show scatter plots colored by species, using orange, teal, and purple to distinguish Iris setosa, versicolor, and virginica. Users can brush a rectangular region in any cell to highlight corresponding data points across all other scatter plots, with brushed circles turning gray. The visualization is built with D3.js v3, using `d3.svg.brush`, `d3.histogram`, and linear scales, rendering as SVG elements.