Fruit flies fight. The males will go after each other, fighting to establish dominance. Edward Kravitz, the George Packer Berry professor of neurobiology at Harvard Medical School, is using the fighting fruit fly model system to explore the neurobiology of aggression. Previously Kravitz has used fighting lobsters to study changes in the brain that occur after fights. While it may sound fanciful, Kravitz's work is serious. "Aggression is a serious problem in society, but even after studies of lots of animal models for many years, we don't know a lot about the biological basis of aggression," Kravitz said.