This example demonstrates a minimal React application that renders the text “Hello React!” centered on the screen. It shows how a functional component, `App`, returns a styled `<div>` element, which is then mounted into the DOM via `ReactDOM.render`. The code uses React 16.13.1 and ReactDOM, loaded from a CDN, with the `className` attribute applying a large, centered font size defined in the accompanying HTML style block. No data or visualization is involved.