React Warning: This JSX uses a plain function. Only React components are valid in React's JSX transform

App.jsx

var React = require('react');
var Yo = require('./Yo.jsx');

var App = React.createClass({
    render: function(){
    return (
        <div>Hello wrold
            <Yo />
        </div>);
    }

});

module.exports = App;

Main.js

var React = require('react');
var App = React.createFactory(require('./components/App.jsx'));

React.render(App(), document.body);
/*
 *  or you can use jsx
 *  But this file need to JSXTransformer
 */
 
var React = require('react');
var App = require('./components/App.jsx');

React.render(<App />, document.body);

Yo.jsx

var React = require('react');

var Yo = React.createClass({

    render: function(){

        return (
            <div>Yo man hello yo </div>
        );
    }
});

module.exports = Yo;