LEDs are commonly used in all kinds of applications. The tiny red and green indication lights found here and there on electronic equipment such as TVs and computers are LEDs. They are very efficient in converting an electric current directly into light, but their use was limited by technical constraints preventing the creation of colors other than red and green. In the 1990s, LED color display was made possible by the development of blue LEDs, and we are now witnessing rapid growth in LED applications. The outdoor displays you see on the sides of buildings and other locations on city streets use LEDs. They are also employed in the optical scanning units of color copying machines and image scanners.