This interactive tree diagram visualizes the hierarchical classification of animals, from the root "Animals" down to specific groups like Mammals and Insects. Built with D3 version 3.5, it uses the `d3.layout.tree` and `d3.svg.diagonal` APIs to create curved links and collapsible nodes, with user clicks toggling child visibility. Node and link styling is defined via CSS, and the static data is embedded directly in the JavaScript.