Aerogel is a low-density solid-state material derived from gel in which the liquid component of the gel has been replaced with gas. The result is an extremely low density solid with several remarkable properties, most notably its effectiveness as an insulator. It is nicknamed frozen smoke, solid smoke or blue smoke due to its semi-transparent nature and the way light scatters in the material; however it feels like extruded polystyrene to the touch.

Aerogel was first created by Steven Kistler in 1931, as a result of a bet with Charles Learned over who could replace the liquid inside a jam (jelly) jar with gas without causing shrinkage.

Silica-based Aerogel is the world's lowest-density solid. Silica Aerogel strongly absorbs infra-red radiation. It allows the construction of materials that let light into buildings but trap heat for solar heating. It has extremely low thermal conductivity (0.003 W/(m·K) [1], which gives it remarkable insulation properties. Its melting point is 1,200 °C (2,192 °F). Silica Aerogel holds 15 entries in the Guinness Book of Records for material properties, including best insulator and lowest-density solid.

Silica Aerogel can protect the human hand from the heat of a blowtorch at point blank range.

This disc is a solid 1 inch (25.4mm) block of aerogel. It is a little over about 5-7mm high (can vary).