A scatter plot matrix displays pairwise relationships among four Iris flower measurements, with off-diagonal cells showing colored points by species and diagonal cells presenting histograms of each variable. The visualization uses D3 v4 with SVG rendering, employing d3.scaleLinear, d3.axisBottom, d3.axisLeft, and d3.histogram to construct the grid. Color encoding via d3.scaleOrdinal distinguishes Iris-setosa, Iris-versicolor, and Iris-virginica using the classic Iris dataset loaded from a CSV file.