This example shows a hierarchical tree of plant species, with land plants branching into grasses, trees, and flowers, and each category further dividing into specific species like Needle Grass and Sequoia. It uses D3 v5’s `d3.hierarchy` and `d3.tree` layouts to position nodes, and renders the structure as SVG with curved paths linking parent and child nodes. Circle size reflects the `value` property of each node, while colors from the data’s `type` and `level` fields drive stroke and fill styling.