SOURCE

$('#container').jstree({
  "core" : { "check_callback" : true }, // so that operations work
  "plugins" : ["dnd"]
});

<div id="container">
  <ul>
    <li data-jstree='{"opened":true}'>Root node
      <ul>
        <li>Child node 1</li>
        <li>Child node 2</li>
      </ul>
    </li>
  </ul>
</div>