Membrane signaling proteins provide the molecular basis for many neurological functions and the pathophysiology of many neurological and neuropsychiatric diseases. However, it remains a major challenge to fully elucidate the dynamic molecular processes of their assembly and function and to interpret those properties in the context of cellular, synaptic, circuit, and behavioral function. G protein-coupled receptors (GPCRs), which serve as the largest family of drug targets in biology, provide a particular challenge because of their complex activation and signaling properties, expression patterns, and diverse roles in neurophysiology and behavior. The Levitz lab uses high-resolution optical and chemical methods, including development of chemical optogenetic tools and single molecule fluorescence-based assays, to elucidate the fundamental biophysical processes that drive receptor function and to gain a deeper understanding of the role of individual receptors and downstream effectors in synapse function and disease.