For many decades, research on the senses has provided a window into the brain. Appropriate stimuli are relatively easy to generate, and the assays — at the level of a cell, a circuit, or a psychophysical percept — can be closely correlated with the stimuli. In recent years, sensory physiology has expanded both down and up: to the cell and molecular biology of receptor cells, and to an understanding of high-level coding and perception. In this issue, 17 papers explore a startling range of approaches to some of the fundamental questions of sensory physiology: How is the energy associated with events in the world transduced into neural signals? How are those signals processed by the nervous system? How does that processing give rise to perception and its behavioral consequences?