In the typical React dataflow, [props](/react/docs/components-and-props.html) are the only way that parent components interact with their children. To modify a child, you re-render it with new props. However, there are a few cases where you need to imperatively modify a child outside of the typical dataflow. The child to be modified could be an instance of a React component, or it could be a DOM element. For both of these cases, React provides an escape hatch.
## The ref Callback Attribute
React supports a special attribute that you can attach to any component. The `ref` attribute takes a callback function, and the callback will be executed immediately after the component is mounted or unmounted.
When the `ref` attribute is used on an HTML element, the `ref` callback receives the underlying DOM element as its argument. For example, this code uses the `ref` callback to store a reference to a DOM node:
React will call the `ref` callback with the DOM element when the component mounts, and call it with `null` when it unmounts.
Using the `ref` callback just to set a property on the class is a common pattern for accessing DOM elements. If you are currently using `this.refs.myRefName` to access refs, we recommend using this pattern instead.
When the `ref` attribute is used on a custom component, the `ref` callback receives the mounted instance of the component as its argument. For example, if we wanted to wrap the `CustomTextInput` above to simulate it being clicked immediately after mounting:
You may not use the `ref` attribute on functional components because they don't have instances. You can, however, use the `ref` attribute inside the `render` function of a functional component:
Your first inclination may be to use refs to "make things happen" in your app. If this is the case, take a moment and think more critically about where state should be owned in the component hierarchy. Often, it becomes clear that the proper place to "own" that state is at a higher level in the hierarchy. See the [Lifting State Up](/react/docs/lifting-state-up.html) guide for examples of this.