A fundamental goal of neuroscience is to understand the molecular, cellular and activity-based mechanisms that control the formation and maintenance of neural circuits and determine how these mechanisms become compromised in neurodevelopmental, psychiatric and neurodegenerative disorders. Over the past four decades, molecular neuroscientists have identified key molecules and mechanisms that underlie synapse development, activity and stability. Meanwhile, the identification and characterization of different cell types has been transformed by single cell profiling techniques and study of neuronal circuits has been revolutionized by new optical methods to visualize, map and control circuits in living animals. Finally, there has been an explosion in the ability to identify genes associated with neurodevelopmental and psychiatric disorders and neurodegenerative diseases. Increasingly sophisticated animal models are proving useful to understand how dysfunction of affected genes and proteins contributes to disease pathology. Although researchers in all of these disciplines are studying the same fundamental issues, no small highly interactive “Keystone-style” meetings bring these three groups together in the same room. In the belief that mutually beneficial insights will emerge from discussing each other’s work, this symposium will bring together leaders working on neuronal development, synapse development and plasticity, circuit structure and function, and the study of brain disease.