This interactive tree visualization displays the hierarchical structure of MeSH (Medical Subject Headings) data, with nodes representing terms and branches showing parent-child relationships. Users can click nodes to collapse or expand subtrees and navigate through the hierarchy. Built with React and d3.v6, the visualization uses SVG rendering with smooth 250ms transitions, `root.descendants()`, and `tree(root)` for layout computation. Node circles scale based on child count, and click events trigger nested navigation through a node stack while a tooltip shows the selected term's name and key.