This example displays a large, centered “Hello !” message rendered as a React component. It uses React 16 and ReactDOM to mount the component into a root div, while D3’s `select` API is imported but not actively applied. The styling comes from a CSS class that sets the font size to 13em, making the text prominently fill the viewport. The rendering approach relies on React’s declarative JSX and the production builds of React and ReactDOM loaded via external scripts.