The Blank Slate: Do You REALLY Know Photoshop

I realized a few days ago, that I've been working with Adobe Photoshop for about 15 years... That is a pretty long time to get to know something. But what I also realized is that I'm still learning Photoshop. There are still tips, tools and techniques that I pick up from time to time that I knew nothing about. It's fascinating to me that a single piece of software can be so vast. Photoshop is one tool for photographers, and a completely different tool for illustrators and designers. This brought a question to my mind...

Knowing Photoshop

What have you recently discovered in Photoshop that you didn't know was there? Have you found something that has helped your work flow, or maybe something that is simply a cool effect or neat trick? Share your discovery with the community, and let's see what kind of list we can build of useful PS tricks and tools... Ready, set, go!