Aerogels are defined as a highly porous lightweight solid that is formed by taking the particles of a gel and replacing them with gas. This "solid foam" that is created generates a network of very small structures that give the gels a porosity and essentially create a lattice shell out of the solid structure remaining.  These Aerogels can be made out of a wide variety of substances, however the most common is silica. Aerogel is nicknamed “frozen smoke” and is made by extracting water from a silica gel, then replacing it with gas such as carbon dioxide  Aerogels are a porous yet solid material that have many material properties that can be used for various applications, but Aerogels are most known for being the lowest density solid ever produced.

Video of Aerogel Overview