This example displays a large, centered “Hello React!” message rendered as plain text on a blank page. It demonstrates the basic setup of a React application using `ReactDOM.render` to mount a functional component into the DOM. The component returns a simple `<div>` with a CSS class that sets the font size to 13em, making the greeting visually prominent. The code relies on the React and ReactDOM libraries from unpkg, and the styling is defined inline within the HTML file.