This scatter plot matrix visualizes the Iris dataset, showing pairwise relationships between sepal length, sepal width, petal length, and petal width, with points colored by species. Using D3.js v5, the matrix displays scatter plots for off-diagonal cells and histograms along the diagonal, enabling comparison of feature distributions. The code implements d3.brush for interactive selection, d3.scaleLinear and d3.scalePoint for positioning, and d3.histogram for binning diagonal distributions. A legend with colored dots identifies the three Iris species, rendered as SVG elements.