This interactive collapsible tree visualizes a hierarchical structure of medical terms derived from MeSH data. The visualization displays the tree as an SVG graphic, with nodes representing medical concepts and connections illustrating their relationships. Users can click on nodes to expand or collapse subtrees, while a dedicated info panel shows the term’s name, key, and description. Built with D3.js v6, the tree uses animated transitions via `transition()` and `attrTween` to smoothly reposition nodes and links. The code implements a custom `convertToHierarchy` function to transform flat JSON data into a nested tree structure.