I know you're all going to laugh at me, but:
Back in the whole craze of those "Magic Eye" paintings, where the image is just a repeating plain background, but you cross your eyes just right and then a 3-d image of a dinosaur or whatever pops out at you, I used to get really surly and grumpy because I could NEVER see the actual 3-d image. I'd cross my eyes until they hurt, and never get anything, and then someone else would look at it and go "oh cool, it's a dinosaur." Eventually I just stopped trying, feigned disinterest, and was glad when the whole "Magic Eye" craze died down.
Well, today's APOD was actually a discussion of the Holographic Principle, oddly using a Magic Eye picture as the photo itself. I'm not sure what made me painfully cross my eyes at it, but I tried once again, in vain, to get something meaningful to pop out of the op-art-ish background.
And then a teapot popped out of the picture at me, plain as could be.
Charmed, I stared at it a while and then realized that I was able to unfocus and refocus my eyes and retrieve the 3-d image. And then I found a bunch of other examples of autostereograms, and sure enough, with a small effort found a cat, a car, a bunny rabbit, a guy sitting at a computer, and yes, a dinosaur. I feel like I've suddenly trained my brain to do a new thing, and I'm oddly excited about it.