Since this is a full-spectrum LED grow light, you get a VEG and BLOOM lighting option. The VEG light can be turned on with a switch during the vegetative phase of your plants. This is the cooler blue spectrum of sunlight which ensures that your plants get a good growth during the early stages. As your plants mature, they need warmer sunlight - which is the red spectrum and found in the BLOOM mode. You will be required to turn on the BLOOM lighting when your plants enter the flowering phase.