This visualization displays an adjacency matrix of high-tech firm connections, using a CSV dataset with source and target nodes. The square grid uses steelblue cells to indicate existing links and white cells for absence, with hover tooltips revealing specific node pairs. The code builds the matrix from flat data, assigns each row and column to a firm, and labels both axes. It renders with D3 v7 SVG elements, using `data.flatMap` and `Array.from` to extract unique nodes and constructing the binary matrix before drawing cells at a fixed 35-pixel size.