Aerogel is a class of materials characterized by its extreme lightweight, and solid state. It is made by replacing the liquid of a gel with gas. First developed in the 1930's, it has seen a revitalization since being used by NASA. Experiments have shown that "producing aerogel in a weightless environment can produce particles with a more uniform size and reduce the Rayleigh scattering effect in silica aerogel, thus making the aerogel less blue and more transparent. Transparent silica aerogel would be very suitable as a thermal insulation material for windows, significantly limiting thermal losses of buildings." -- from Wikipedia.