Display inner DIV within outer DIV without outer DIV expanding (i.e. while hovering over)

Display inner DIV within outer DIV without outer DIV expanding (i.e. while hovering over)

I want to avoid the inner DIV to expand the outer DIV when I hover over the outer DIV and fadeIn the inner DIV. How can I hover over the outer DIV and show the inner DIV without the height of the outer DIV expanding? Thanks for your help!