Via Scott Aaronson and John Baez, a video on how to turn a sphere inside out without cutting or creasing it. I have just finished watching this with my daughter, Zoe. She was fascinated and watched it right through to the end. And, from the comments she made, I got the distinct impression that she was understanding the 3-dimensional moves quicker than I was. I found this a little unsettling: she might actually be brighter than me!