A blue LED (Light-Emitting Diode) emits light in the blue portion of the electromagnetic spectrum with a typical wavelength of between 450 to 470 nanometers. Blue LEDs are used in the creation of white LED lighting which is achieved by adding a layer of phosphor material onto the blue LED which absorbs a portion of the blue light and emits light in other colours including yellow. This process creates white light and is known as phosphor conversion. The composition of the phosphor layer can be adjusted to produce different colour temperatures of white light. Blue LEDs are used in LED backlit LCD screens, OLED displays, signage and advertising, medical and scientific applications such as fluorescence microscopy as well as for simple decorative effect in accent and architectural lighting.