This spinning 40-micron section of rat hippocampus shows new neurons in the granule cell layer of the dentate gyrus. Mature neurons are labeled in green with NeuN and proliferating cells are labeled in red with BrDU. The video was generated by BrainCells Inc, a La Jolla, Calif. company searching for new antidepressant drugs based on their ability to stimulate neurogenesis in the hippocampus. All antidepressants on the market demonstrate neurogenic properties in animals. BrainCells uses images like this to measures changes in proliferation after a candidate compound has been given to rats.