React components and module exports

I don't understand how module.exports can only export one component that has a dependency on a subcomponent but still be rendered in the DOM although that sub component was never exported.

//component.js

var SubComponent = React.createClass({
...
    });

var Component = React.createClass({
    ...
    render: function () { 
    return(
        <div><SubComponent /> stuff</div>`)
        }});

module.exports = Component

//main.js

    var Component = require('./component.js');

    var MainContainer = React.createClass({
    render: function () {return (
    <Component />)
    }})