We want to learn how neural circuits are assembled in young animals and how they process information in adults. A particular focus is identification and analysis of synaptic recognition molecules responsible for the amazing specificity of connections that underlies complex neural processing. We use a combination of genetic, molecular, histological and electrophysiological approaches to address these issues. Our main model system is the mouse retina because, although it is about as complicated as any other part of the brain, it has numerous advantages that facilitate analysis. We believe that our methods and results will be useful in tackling less accessible parts of the brain such as the cerebral cortex.