Customized Tooltips

I would like to create a custom tooltip, which uses multiple UnityGUI components. Does GUIContent allow this? Or do I need to create my own mouseover handler which creates and draws the tooltip? Thanks!

Further detail... I'd like to be able to position and format the elements on the tooltip. So maybe 1 label is bold, the image is in the top left corner, another label is normal and so on.

http://unity3d.com/support/documentation/ScriptReference/GUI-tooltip.html