Grow lights are artificial light sources, usually electric, designed to stimulate plant growth by emitting an electromagnetic spectrum suitable for photosynthesis. Grow lights are used in applications that do not have natural lighting or require supplemental lighting. For example: In winter, when possible daylight hours may not be sufficient for desired plant growth, lights are used to extend the time plants receive light. If the plants don't get enough light, they will grow leggy. Growing lights either try to provide a spectrum similar to the sun, or a spectrum better suited to the needs of the plant being cultivated, a spectrogram. Simulate outdoor conditions with different color, temperature, and spectral output from grow lights, as well as vary the lumen output (intensity) of the lights. Depending on the type of plant being cultivated, the cultivation stage (such as germination/vegetative or flowering/fruiting period) and the photoperiod required by the plant, the specific range of the spectrum, luminous efficiency and color temperature are desirable for the specific plant and time period.