[jQuery] height of hidden element

[bob]

content for "hidden_el" is loaded by Ajax from random source
so the height of that element is not known up front.

I would like to use "animation" function to show element(expand) on
mouseover.

How do I find out the height of that element(final height for
animation purposes)
when content is already loaded but it is hidden?


<span id="show_el">Show element</div>
<div id="hidden_el" style="display:none"></div>

jq('#show_el').mouseover(function(){

        jq('#hidden_el').css({height: 0}).animate(

                {height: ??????????},

                { duration: 200, queue: false, easing:
'easeOutBounce',complete:function(){ //some callback here} }

        );

}