Horticultural crop production plays an important role in the global food supply, and horticultural plants contain numerous health-promoting phytochemicals, such as vitamins, flavonoids, polyphenols, and other secondary metabolites. The formation of yield and nutritional quality depends on the intrinsic characteristics of horticultural crops and environmental conditions. Light is the primary energy source for photosynthesis, and light, ranging from UV to far-red, is a critical factor in regulating plant growth, morphogenesis, development, and metabolic processes. The physiological and molecular regulation of plant processes is related to the intensity, spectrum, direction, photoperiod, and timing of light. And light is the most important environmental factor determining the yield and quality of horticultural crops.