visualy browsing posts in a category ? (yeh the title sucks…)

Ok i’m tryin to do somethin and i’m pretty new to those things so i’m gonna try to be clear :

Actually i have a (left) sidebar, and there is a category list. So you can click on one of the listed categories and the post appears (at the right)… no surprise ok.

Now what i would like is when you click on one categories you have a list of thumbnails that appear at the right (where the posts appeared previsouly). Then you click on one of the thumbs – each one representing one post – and then ‘bang’ you have your post.

I have no idea how to achieve this, i don’t even know if its possible so some help would be much appreciated, thanks.