What is Aerogel?

"Aerogel is a synthetic porous ultralight material derived from a gel, in which the liquid component of the gel has been replaced with a gas.The result is a solid with extremely low density and low thermal conductivity. Nicknames include frozen smoke, solid smoke, solid air, or blue smoke owing to its translucent nature and the way light scatters in the material. It feels like fragile expanded polystyrene to the touch. Aerogels can be made from a variety of chemical compounds.
Aerogel was first created by Samuel Stephens Kistler in 1931, as a result of a bet[citation needed] with Charles Learned over who could replace the liquid in "jellies" with gas without causing shrinkage.
Aerogels are produced by extracting the liquid component of a gel through supercritical drying. This allows the liquid to be slowly dried off without causing the solid matrix in the gel to collapse from capillary action, as would happen with conventional evaporation. The first aerogels were produced from silica gels. Kistler's later work involved aerogels based on alumina, chromia and tin dioxide. Carbon aerogels were first developed in the late 1980s.[citation needed]
Aerogel does not have a designated material with set chemical formula but the term is used to group all the material with a certain geometric structure."
See more @ Wikipedia

More Info...

1. Aerogels: Thinner, Lighter, Stronger @ NASA
2. QUEST Lab: Aerogel - KQED QUEST