title: how to add a second grid under a tab in magento admin?
body: <p>I'm working on a new Magneto module.<br>
  For my Admin panel i've made a Grid "A" and i want to add a Grid "B" under one Tab of the Grid "A".<br>
  Just like the Upsells Grid under the Products Grid.<br>
  I've made many search but i didn't find something interesting.  </p>
  
  <p>Thanks for your help   </p>