In order to achieve this, we are making use of the render() method of ReactDOM. Additionally, we need a root node or a mount node to render a React element. This node works as a placeholder and informs React where the element should be rendered to. Theoretically, there can be many different root nodes in the HTML document. React controls these independently and keeps track of the different mount nodes. So instead of having one large React application, you could easily choose to have many smaller (or larger) apps in a single HTML document. In most situations, you are likely to only have a single root node for your React application.