Check out this contender for the title of 'world's lightest solid.' To demonstrate just how light it is, Zhejiang University in China, where the material's creators are based, has published pictures of chunks of it perched on small leaves, held aloft by grass seedheads and floating on the stamen of a cherry blossom.
It's still in its earliest stages of development, but in the future, the new material (dubbed carbon aerogel) could be designed to soak up oil spills or clean other pollutants. The materials used now to clean up spills absorb 10 times their weight in oil, but the new stuff can handle 900 times its weight in oil.