This chapter discusses retinal function, where primary function of retina is to translate visual stimuli into the language which the nervous system understands. The shape of the outer segment is somewhat different in rods and cones, and is as suggested by their names. The synapses between the receptor cells and bipolar cells are influenced by horizontal cells which interconnect neighbouring areas of the retina. The retina is so positioned in the eye that light has to pass through the ganglion cells and bipolar cells before reaching the rods and cones. Cone pigment is of three types, and accordingly there are three types of cones. Photo-activated rhodopsin quickly decomposes into 11-cis-retinal, a vitamin A derivative, and opsin, a protein. Photo-activation of the rhodopsin molecule is accompanied by a conformational change, which in turn brings about a similar change in a membrane protein, transducin, in the plasma membrane of the outer segment.