如何只使用CSS在div的鼠标悬停中弹出一个单独的div ?

I have a small gallery of thumbnails. When I place my mouse pointer over a thumbnail image I'd like to have a full size image pop up in a div in the top right of the screen. I've seen this done using just CSS and I'd like to go down that route rather than use javascript if possible.I have a small gallery of thumbnails. When I pl