The scientific community has long held the belief that once neurons have perished, they cannot be replaced. Other bodily cells, such as skin and blood cells, are replaced when their stem cells divide to produce new skin and blood cells. It was considered that neurons lacked their reservoir of stem cells.Fernando Nottebohm of Rockefeller University questioned this belief in the 1980s, discovering stem cells in the adult brains of songbirds. Neural stem cells are the name for these stem cells. Since then, neural stem cells have been discovered in rats, mice, monkeys, and even humans.