Want to own a small piece of something truly cool? Comprised of 99.8% air and weighing in at only 3 milligrams per cubic centimeter (.00011 pounds per cubic inch), AeroGel has been recognized by Guinness World Records as the world's lightest and lowest density solid. This next-generation material is made by extracting the liquid component of a silica gel though a process known as supercritical drying, which results in a transparent Frozen Smoke. It's not only extremely light, it's also highly porous, super absorbent, and the world's best thermal insulating solid. It's currently being used by NASA for collecting comet samples and interstellar dust and as the insulating material aboard the Mars rover.
Aerogel - World's Lightest and Lowest Density Solid