Light-emitting diodes are semiconductor elements that emit light when voltage is applied, and they are characterized by low cost and durability. For many years only red light was possible, but Shuji Nakamura of Nichia Corporation succeeded in making a diode that emits blue light with the use of gallium nitride (GaN). These blue LEDs are already used in traffic signals and neon signs, and applications in next-generation DVDs and other products are promising.