Aerogel.

I'm sure that those of you with more than a passing interest in materials research are already familiar with this, but I found it quite remarkable. Aerogel is a substance with a crystaline structure which shatters like glass. What's so special about it? First of all, Aerogel consists of about 99.8 percent air. This makes it extremely light weight yet durable and gives it tremendous capacity for insulation. The stuff was invented in 1931, but until recently was very expensive to make and mass produce, and couldn't be made into flexible forms such as housing insulation and clothing. Here are some other photos, and an article on NASA's recent use of the material to capture particles from a comet.