Imagine a shoe so uncomfortable you have to hammer the insole and smash it inside a door to make it tolerable. Now imagine tossing the same $70 shoe in the trash because it shredded into pieces after just 45 minutes. Welcome to the world of ballet.

In its raw form, d3o looks like slime and molds like Play-Doh, but take a hammer to a clump and it changes to a stiff rubber. This curious substance introduced itself in the 2006 Olympics as a safety lining for the Spyder skiing suits, and that same year, d3o's protective ski hat won PopSci's Best of What's New Award.