class Container extends React.Component {

   constructor(props){

     super(props);

   }

   componentDidMount(){

     console.log('componentDidMount', this.props.children);

     React.Children.forEach(this.props.children, (child, index)=>console.log(ReactDOM.findDOMNode(child)))

   }

   render(){

     return (

       <div>{this.props.children}</div>

     );

   }

}

​

ReactDOM.render(

  <Container>

    <div>hello</div>

  </Container>, 

  document.querySelector('.main-container')

);