Smart materials - Off and on reflection

Smart materials, which can change their physical properties, enable a building to adjust its environment to the prevailing conditions. A new addition to their number is the switchable window -- a sandwich of glass, thin metal-hydride films and some medium for delivering hydrogen gas, which can be reversibly converted from reflecting to transparent states. When the technology has improved to allow electronic switching, instead of requiring direct pumping of gas, such switchable windows might be used in energy-conscious building design -- and for the lazy, they would make a good alternative to curtains.