It’s as light as air and feels like styrofoam to the touch. But drop it on a table and you’ll hear a ping and acoustic resonance like crystal glass. Put an ice cube on top of it, place it over an intense flame, and the ice won’t melt.
Discovered nearly 80 years ago, aerogel is an open-celled material comprised of more than 95 percent air. Similar in chemical structure to glass, aerogels have gas or air in their pores instead of liquid. With individual pores only a few nanometers wide, it has the lowest thermal conductivity of any known solid.