The nervous system regulates our mind and behavior. Precise regulation of each neuron and connections between neurons is required for the proper functioning of the brain. Therefore, elucidating the mechanisms regulating brain function facilitates the development of therapies for neurodevelopmental and neurodegenerative diseases such as Parkinson’s and Alzheimer’s disease. We study how neurons, the connections between neurons, and adult neurogenesis contribute to the functions of the nervous system, from the perspective of cell biology.