Sometimes, we manage observable data or only data that is handled asynchronously by our component class, and we need to ensure that our views promptly reflect the changes in the information once the observable field changes or asynchronous loading has been accomplished after the view has been rendered. The async pipe subscribes to an observable or promise and returns the latest value it has emitted. When a new value is emitted, the async pipe marks the component to be checked for changes. We will return to this concept in Chapter 7, Asynchronous Data Services with Angular.