SignificanceAn increasing number of therapeutic strategies are being designed and tested in animal models for numerous forms of hereditary deafness, the most frequent genetic sensorineural disorder. One major challenge is the implementation of these therapies for diverse isolated and syndromic forms of hearing loss, taking into account the spatial and temporal patterns of expression of the causal gene in the auditory sensory organ, the cochlea. Here, combining single-cell and single-nucleus RNA sequencing with in situ RNA hybridization assays, we present a large-scale single-cell transcriptomic atlas for three crucial stages in the maturation of the mouse cochlea. This detailed atlas of gene expression provides key information for the development of effective therapeutic approaches.