A photobioreactor system for mass production of microorganisms is disclosed. Water with microorganisms suspended therein is sprayed through a nozzle to create droplets. These droplets have a high surface area to volume ratio enabling efficient light transfer and gas diffusion. The water may also be passed through channels between two transparent plates, wherein superior mixing is achieved along with a high surface to volume ratio. The water is preferably circulated through a dark holding tank Active and passive flashing lights of different wavelengths are used to promote growth of the microorganisms when the water is sprayed and/or passing through the transparent plates.