“Scientists at Zhejiang University in China have developed a new kind of ultra-light material called carbon aerogel. This solid material has a density of only 0.16 mg/cm3, one-sixth that of the air. It is now recognized as the new world’s lightest material.”
http://www.designfax.net/cms/dfx/opens/article-view-dfx.php?nid=4&bid=259&aid=2007&et=materials&pn=01