A fundamental goal of neuroscience is to understand the molecular, cellular and activity-based mechanisms that control the formation and function of neural circuits and determine how these mechanisms become compromised in neurodevelopmental, psychiatric and neurodegenerative disorders. Over the past two decades, molecular neuroscientists have identified key molecules and mechanisms that underlie synapse development, activity and stability. Meanwhile, the study of neuronal circuits has been revolutionized by new methods to visualize and map circuits in living animals, as well as the development of approaches to control neuronal activity. Finally, disease researchers have identified genes associated with neurodevelopmental and psychiatric disorders and neurodegenerative diseases. Animal models of these diseases are proving useful to understand how dysfunction of affected genes and proteins contributes to disease pathology. Although these fields are working on the same process, no small highly interactive “Keystone Symposia-style” meeting brings these three groups together in the same room. This symposium will bring together leaders working on synapse development and function, circuit structure and function, and the study of brain disease, believing with confidence that mutually beneficial insights will emerge from discussing each other’s work.