If you want the HTML representation of a React element you can use #renderToString or #renderToStaticMarkup.
import ReactDomServer from 'react-dom/server';
ReactDomServer.renderToString(<div>p</div>);
ReactDomServer.renderToStaticMarkup(<div>p</div>);
will produce
<div data-reactid=".1" data-react-checksum="-1666119235">p</div>
and
<div>p</div>
respectively. You will however not be able to render the parent as a string from within itself. If you need the parent too then from where you render the parent pass a renderToString version of it as props to itself.