The molecular mechanisms underlying the development and functioning of the auditory system remained virtually unknown until genetic dissection emerged as a means of accessing them. In this lecture, I will show why and how the genes responsible for deafness in humans made it possible to bring the auditory system into the molecular era. I will focus, in particular, on the biology of the auditory sensory cells. I will show how the molecular mechanisms underlying the essential functions and properties of these cells —auditory sensory transduction, the generation of sound distortions and the temporal precision of their activity — were elucidated and how the role of previously neglected structures was discovered. Our recent results, notably, demonstrate that some of these forms of deafness are not exclusively peripheral in origin, indicating that the proteins encoded by some deafness genes are also involved in auditory cortex development. In parallel, this work has also shed light on the pathogenesis of a very large number of forms of deafness, most of which are hereditary. Based on these data, active research with the aim of curing hearing impairment is currently underway. We will look at the preliminary results obtained in animals and the challenges that lie ahead.