Researchers at the University of California and Lawrence Berkeley National Laboratory have discovered an inexpensive material that could lead to highly efficient windows for automobiles and buildings. Robert Kostecki and Frank McLarnon made the discovery while working with an electrode consisting of thin, transparent films of nickel hydroxide and titanium dioxide. They sandwiched the two materials on glass, which darkened when exposed to a UV light source. After further investigation, the researchers surmised that the material could be made to change from transparent to opaque and back again when the light was removed.