CCT stands for Correlated Color Temperature, which is a measure of how yellow or blue the color of light emitted from a light bulb appears. It is measured in Kelvin (K), which is similar to degrees in Celsius. Different temperatures on the Kelvin scale represent different colors. Warm light sources, such as incandescent bulbs, have a low color temperature (2200-3000K) and feature more light in the red, orange, and yellow range. Cool light sources, such as some HID or fluorescent lamps, have a high color temperature (>4000K) and feature more light in the blue range. The most common CCT is between 2200K and 6500K, and the higher the Kelvin level, the whiter the light. When selecting CCT, it is important to consider the atmosphere you are trying to create and the type of environment in which the lighting will be used. For example, a low, warm CCT is common in a relaxed environment, such as a home living room or nursery, while a higher CCT (natural or cool white) is best in an office or warehouse where visibility is crucial.