LED (Light Emitting Diode), light emitting diode, is a solid-state semiconductor device, it can directly convert electricity into light. Heart of the LED is a semiconductor chip, the chip attached to a bracket on the end, is negative, the other end of positive pole of the power supply, the entire wafer was encapsulated by epoxy resin. Semiconductor chip is composed of two parts, the part of the p-type semiconductor, in the dominant position it inside the hole, and the other end is the n-type semiconductor, here is mainly electronic. But when I connect the two semiconductor, they formed a "p-n junction". When a current passes through the wire act on the chip when electron is pulled into a p-region, electrons with holes in the p-compound then energy as a photon, which is the principle of LED light. And the wavelength of the light determines the color of the light, is decided by the p-n junction formed material.