Jquery - slideDown with existing height

If i have a div with a class that sets the height 100px, and overflow:hidden (effecti开发者_开发知识库vely a preview of it's contents), how can i incorporate the 'slideDown()' method to slide to the full height of the div? (i.e. remove the height restriction in the css class).

found answer here: http://sim.plified.com/2008/09/15/sliding-content-from-a-partial-height-with-jquery/