Aerogel - best insulator and lowest density solid

 

Aerogel (also called 'frozen smoke' because of its hazy blue appearance), is a truly remarkable material. It is the lightest and lowest-density solid known to exist, and holds an unbelievable 15 entries in the Guinness Book of World Records, including best insulator and lowest density solid. Aerogel is composed of 99.8% air and is chemically similar to ordinary glass.

Being the world's lightest known solid, it weighs only three times that of air.