This photo taken at Zhejiang University on March 19, 2013, shows a graphene aerogel, the world's lightest solid material - developed by the nanometer-macromolecule research group of the university. It was sold for 10 million yuan (1.6 million dollars) at an auction of scientific achievements in Hangzhou city, capital of East China's Zhejiang province, on July 1.[Photo/IC]