Adobe PhotoShop - Take Snapshots Of Your Work For Precautionary Measures (Photoshop 6.x/7.x/CS)
When you're working on an extensive project in Photoshop, it's always a good idea to take a few snapshots as you go. That way, if you want to backtrack or something goes awry, you can click on a snapshot and get to work again. To create a snapshot, open the History palette and click the Create New Snapshot button at the base of the palette (it's the little camera icon). Upon doing so, Photoshop places a saved version of your file in the History palette. Then, if you need to access that image, just click on it.