Hearing impairment is primarily attributed to inner ear hair cell (HC) defects that subsequently lead to spiral ganglion neuron (SGN) loss. The HC loss cannot be self-repaired because of the HCs' limited capacity to regenerate in mammals. Atoh1, also known as Math1, Hath1, and Cath1, is a proneural basic helix-loop-helix (bHLH) transcription factor that played a major role in HC differentiation. Atoh1 activity at various developmental stages can sufficiently drive HC differentiation in the cochlea. Recent issues of a certain publication have identified that Atoh1 is essential for inner ear development, such as cell growth, morphogenesis, differentiation, cellular maintenance, and survival. We summarize the new findings in Atoh1 research and identify the mechanisms underlying the role of Atoh1 in HC regeneration to launch the future of Atoh1 therapy.