Getting DOM node from React child element

this.props.children should either be a ReactElement or an array of ReactElement, but not components.

To get the DOM nodes of the children elements, you need to clone them and assign them a new ref.

render() {
  return (
    <div>
      {React.Children.map(this.props.children, (element, idx) => {
        return React.cloneElement(element, { ref: idx });
      })}
    </div>
  );
}

You can then access the child components via this.refs[childIdx], and retrieve their DOM nodes via ReactDOM.findDOMNode(this.refs[childIdx]).