Producing an LED starts with a substrate. The substrate is sapphire for InGaN LEDs or gallium arsenide for AlInGaP LEDs. Layers of various materials are then grown on the substrate. These layers are applied under precise pressure and temperature control, and make up the "N layer" or active region and the "P layer". This process is called epitaxial or epi-growth. The brightness, color and intensity of the resulting LED are determined by the quality and consistency of this epigrowth process. After the epigrowth process individual LED chips are defined on the wafer. The wafer is then sawn up in to separate individual LEDs whose exact color and electrical characteristics are then recorded. Finally, the LED is installed in the LED package where wire bonds create the electrical connections. To complete the package, a lens is attached to direct light and silicon is added to protect the chip and fill the air gap between the chip and lens. Each LED is then tested and organized according to color, brightness, and other characteristics.