React DevTools

React DevTools is a browser extension available for Chrome, Firefox, and Edge that allows developers to inspect a React tree, including component hierarchy, props, state, and hooks. This tool is highly recommended as it makes debugging easier by providing views of the component tree on the current page and the current state and props of each component.

Additionally, React DevTools provides performance profiling, helping developers understand why the application is slow by identifying parts of the application that are computationally expensive. The developer can see when components mount, update, and unmount, how much time each rendering takes, and what triggers each rendering.

Any changes made in the DevTools will be instant, allowing the developer to test different states of the application before implementing them in code.

Here is how to use it:

1. Install the React DevTools extension in your browser.
2. Open the developer console in your browser (F12 in Chrome)
3. Switch to the new 'React' or 'Components' tab that has appeared.

No code snippet is required as React DevTools is a browser extension and not code that you would include in your app. However, once installed, you can view your components like this:

```
<ComponentName props={...props} state={...state} />
```

You can click on each component to see its state and props detailed on the side.
This tool does not require you to change or add anything to your application code—it works with any React application out of the box. It also operates with both functional and class components.