The inner ear balance organ, the utricle, requires mechanosensitive sensory hair cells, much like those in the hearing organ, to function. Because the mammalian hearing organ does not regenerate, hearing loss is permanent. On the other hand, there is a low level of regeneration in the utricle. Using both mouse and human inner ear tissues, we have identified and been characterized such sensory cell progenitors. Specifically, we have been studying their degree, time-course, and mechanisms of regeneration. Importantly, we also compare regeneration at the histologic level to physiological recovery at the cellular and whole animal levels. While our short-term goal is to understand the mechanisms of hair cell regeneration, our long term goal is to enhance regeneration in humans to recover lost balance and hearing functions.