For a long time, aerogel was the lightest and least dense material ever made. Late last year, a metallic lattice structure took the crown. And today, the new champion is officially aerographite, with a density so low that it barely exists at all.
The density of aerographite is a mere 0.2 milligram per cubic centimeter. For the record, the next best thing (those metallic lattice structures) are three times heavier at about 0.9 milligram per cubic centimeter. This stuff is more or less entirely made out of air, with what little structure there is consisting of a network of hollow carbon tubes grown at nano and micro scales, which you can see in the electron microscope image above. A clump of it would look something like black sponge, appearing completely opaque despite its absurdly low density (unlike aerogel).
Despite the fragile look, aerographite has some impressive structural properties. You can compress it down to make it 1,000 times smaller, and it'll spring right back to its original size when you let go. It can also support over 40,000 times its own weight, which is 35 times better than aerogel can do.
Aerographite was created by researchers at Hamburg University of Technology and the University of Kiel, who suggest that a good application for this stuff might be as "electrode materials for the increasing demand of batteries and high surface area supercapacitor materials." That's fine, I guess, but just tell me how much it'll cost me to get a blob of aerographite to mess with on my own.