A treatment method that overturns a common sense of the medical community that "the brain cell does not regenerate" has been developed in Japan, and its practical application is imminent. The key to the treatment are "stem cells", which regenerate various body tissues on a daily basis. Japanese researchers have discovered that stem cells, which have been thought to be absent in adult brains, actually exist in small numbers. A therapy that stimulates brain stem cells in an innovative way and regenerates the brain is entering the final phase of a clinical trial.