Righty and lefty, as typified by the dominant hand-use in humans, are actually phenomena found in various animals. It is believed that having a dominant hand maximizes locomotor ability and provides an advantage for survival. However, the differences in the nervous systems between righty and lefty, the developmental process of dominance, what genes and molecules regulate dominance, and when it was established evolutionarily still remain essential mysteries. Using African scale-eating cichlids, which are known for their pronounced handedness, I am investigating the mechanisms governing laterality from multiple approaches, including neuroscience, genomics, behavior, ecology, and evolution.