This interactive tree diagram displays a hierarchical data structure for blood groups, starting with a root "Blood Group" node that branches into types A and B, each further divided into positive and negative variants. Built with D3.js version 3.5.17, it uses SVG rendering and animation, implementing a collapsible tree layout where users can click nodes to expand or collapse child branches with smooth transitions via the `d3.layout.tree` and `d3.svg.diagonal` APIs.