Aerogel is a low-density solid-state material derived from gel in which the liquid component of the gel has been replaced with gas which represents more than 90% of its structure (this is why it is nicknamed frozen smoke, solid smoke or blue smoke.

The result is an extremely low density solid with several remarkable properties, for which it holds an unbelievable 15 entries in the Guinness Book of World Records, including best insulator and lowest density solid. Being the world's lightest known solid, it weighs only three times that of air..It negates just about any kind of energy transfer - thermal, electrical or acoustic. A one-inch thick Aerogel window has the same insulation value as 15 panes of glass and trapped air - which means a conventional window would have to be ten-inches thick to equal a one-inch thick Aerogel window.

Typical “extreme” properties of silica aerogel materials are:

- Aerogels have the lowest thermal conductivity values of any solid
- Aerogels are exceptional reflectors of audible sound, making excellent barrier materials; aerogels have very low sound velocity through structure (~100 m/s)
- Aerogels can be exotic energy absorbers, showing capability to capture high velocity dust particles in space that would penetrate thick steel
- High internal surface areas (up to 1500 m2/g)
- Ultra-low refractive index values for a solid (1.025), approaching that for air
- Ultra-low dielectric constants for a solid (can be < 1.1)