parent child query

do you mean something like?:

<ul>
<% @lists.each do |list| -%>
   <li><%= list.name -%>
   <ul>
   <% list.items.each do |item| -%>
       <li><%= item.name -%></li>
    <% end -%>
    </ul>
   </li>
<% end -%>
</ul>