title: How do I extend in my class a Dom element, in mootools
body: <p>I want to create a Class, say <code>MyDiv</code>, which inherits from the original DOM DIV element. 
  Later in my code I would like to use it like that:  </p>
  
  <pre><code>$('a-container').adopt(new MyDiv('my own set of params'));
  </code></pre>
  
  <p>I am missing the exact syntax to do it.</p>