A new approach to study the function of the retina is described. It involves a precise revealing of synaptic connections between the neurons by means of three-dimensional volume reconstructions. Identification of several hundreds of synapses revealed the existence of groups of synaptically interconnected neurons constituting discrete neural circuits accounting for processing of information contributed by the photoreceptors. Supplementary information contributed by electrophysiological recordings of membrane potentials of neurons in these circuits made it possible to determine how information is processed by the circuits. Two versions of one of the circuits are analyzed in this communication.