Neurodegeneration,a defining hallmark of Alzheimer's disease (AD),features the progressive loss of neuronal structure and functions.Therapeutic approaches to AD show limited efficiency in halting the neurodegeneration to date.Given the lack of neuronal renewability in most subareas of the adult brain,symptomatic drugs or treat-ments cannot repopulate neurons and rewire the degener-ated neuronal circuits in AD.Introducing new neurons into AD brains,by either promoting innate hippocampal neurogenesis,transplanting external cells,or in vivo glia-neuron conversion,shines new light on AD treatment.