The behavior of an organism relies on the function of neural circuits. Neural circuits comprise complex ensembles of neurons interconnected through precise patterns of connections called synapses, specialized structures that underlie the regulated flow of information in the brain. How precise patterns of synaptic connections emerge during development and how these circuits control specific behaviors remain exciting frontiers in neuroscience. To gain insight into neural circuit function and development, scientists have turned increasingly to genetic technologies to manipulate specific cells within circuits and the function of specific genes in a model organism, such as a worm, fly, and mouse. In this symposium, recent progress in uncovering the cellular and molecular basis of neural circuit function and development will be presented.