To function properly, cells and tissue must receive and interpret a large variety of signals. They do so, in part, through signaling receptors, some of which reside on cell surfaces known as plasma membranes. We study adrenergic receptors, which are targets of commonly used medicines including alpha and beta blockers. By developing a new class of sensors that allow for detection and visualization of signaling events in living cells, we made the unexpected finding that signaling cues to cells not only act on cell surface receptors but also on internal cellular compartments. This observation raises numerous questions pertaining to fundamental aspects of cell signaling and suggests that cells have spatially compartmentalized signaling hubs. This basic biological insight has clinical implications as well. For example, certain beta-blockers are known to have differential clinical efficacies but the underlying reasons for these differences are not known. We have found that different beta blockers act on distinct hubs of signaling. Beyond their well-established roles in cardiac physiology, adrenergic receptors regulate a wide variety of important physiologically and behavioral processes. We are using our newly developed tools to investigate the consequences of signaling from internal compartments on a range of cellular, physiological, and behavioral outcomes.