Aerogel, AKA "Frozen Smoke"
The phrase "frozen smoke" describes the world's lightest solid material. Known as aerogel, this material is 95-99% air. There are many different kinds of aerogels, made from substances from silica to carbon nanotubes. All of them are incredibly light, because their liquid component has been replaced with a gas. They're typically around 20 times heavier than air, though a silica aerogel has been created that was only three times heavier than air.
Key Facts In This Video
Aerogel has had its liquid component removed, leaving its molecular structure intact. (0:35)
Aerogel can hold up to 4,000 times its weight in force, but it's also very brittle. (1:06)
Aerogel tiles are used in space to collect dust from comets. (1:48)