This example shows a hierarchical tree visualization of COVID-19 data, organizing global regions (Europe, North America, Africa) into countries and their respective cumulative case, death, and recovery statistics. Each node is represented as a circle with text labels, connected by gray links, and rendered as scalable vector graphics (SVG) using the D3.js v7 library. The code constructs the tree layout using the `d3.tree()` and `d3.hierarchy()` functions, and applies custom CSS for node styling. Data is hardcoded within the JavaScript, and the visualization is created by declaring an SVG element when one does not already exist.