The stomatal pores of plant leaves, situated in the epidermis and surrounded by a pair of guard cells, allow CO 2 uptake for photosynthesis and water loss through transpiration. Blue light is one of the dominant environmental signals that control stomatal movements in leaves of plants in a natural environment. This blue light response is mediated by blue/UV A light-absorbing phototropins (phots) and cryptochromes (crys). Red/far-red light-absorbing phytochromes (phys) also play a role in the control of stomatal aperture. The signaling components that link the perception of light signals to the stomatal opening response are largely unknown. This review discusses a few newly discovered nuclear genes, their function with respect to the phot-, cry-, and phy-mediated signal transduction cascades, and possible involvement of circadian clock.