thumbnails and captions?

hi... how would somebody create a thumbnail that has a caption under it and then when clicked on shows a larger size of the same graphic but still shows the caption under it?? havent quite figured that one out yet... thumbnail specs: total size with graphic, whitespace border on all 4 sides and caption at the bottom cant exceed 150px wide and 160.332px tall. thumbnail graphic must be clickable to make image larger (includes caption). enlarged image specs: height: 385px, width: 385px (no more than that to prevent pixelations). the enlarged graphic must be in its own window and include the caption that was on the original page. the enlarged image must have a link somewhere to allow the window to be closed and returns the viewer to the original page that image was on. page specs: 800 wide and 600 tall 20 images a page no less (40 a page if possible but not required). clients preferred graphic/image format: jpg anyways does anybody know how to go about this sort of thing?? or is it sort of unpractical to have thumbnails that small and have captions under them?? (sorry for my stupidness on images but when you cant see them it hurts)...