This example renders a simple “Hello React!” message, demonstrating a React application that integrates D3.js for data processing. The code defines a React class that uses D3’s `csv` function to load a local `celeb.csv` file and then applies D3’s `nest` function to hierarchically group the celebrity data by `category` and `gender`. The nested structure is recursively renamed into a tree format, but the visualization itself is not displayed; instead, the processed data is logged to the console. The app uses React 16.13.1, ReactDOM, and D3 v5.15.0.