title: Can a MongoDB collection have inside it another collection?
body: <p>I need to store a recursive tree structure. A linked list.<br>
  So all the objects are the same. Each has a pointer to a parent object and each has an array of child objects.<br>
  Can I store such a structure in Mongo.<br>
  i.e. A Mongo collection of parent objects, each object holds within it a Mongo collection of child objects.  </p>
  
  <pre><code>$a = $MyCollection-&gt;findOne(**some conditions)-&gt;Childs-&gt;find(...)
  </code></pre>