Apple has announced that Mac OS X 10.7 Lion will include a new feature, similar to the popular Time Machine tool, called Versions. Versions essentially makes a copy of a document/file every time you save it. If you are looking for a respective file and want to see what it looked like you can now do that.
Versions records the evolution of a document as you create it. Mac OS X Lion automatically creates a version of the document each time you open it and every hour while you’re working on it. If you need to revert to an older version or retrieve part of a document, Versions shows you the current document next to a cascade of previous versions — in an interface similar to that of Time Machine — so you can see how your work looked at any given time. You can revert with a click, or quickly copy and paste work from a previous version into the current version.*