This example displays a single, centered “Hello React!” message in a 13-em font. It demonstrates a minimal React setup within a D3 environment, using React 16.13.1 and ReactDOM to render a functional component into the `#root` div. The page loads production React builds via `unpkg.com` and executes the app from a compiled `bundle.js`, showcasing a basic React render without any data or interactive D3 elements.