Thermochromic glass was developed in 2014.
Thermochromic glass uses heat from the sun to tone the glass, thereby making it less heat transmitting. The more direct sunlight the glass is exposed to, the darker the tint. This feature reduces the amount of heat from the sun that would otherwise accumulate in the building.
Thermochromic glass is a type of smart glass, also known as intelligent glass or dynamic glass. Smart glass regulates its transparency, and thereby the amount of light transmitted, by using electric current, light, or heat.