Aggression is an evolutionarily conserved behavior that evolved in the framework of defending or obtaining resources. When expressed out of context, unchecked aggression can have destructive consequences. Model systems that allow examination of distinct neuronal networks at the molecular, cellular, and circuit levels are adding immensely to our understanding of the biological basis of this behavior and should be relatable to other species up to and including man. Investigators have made particular use of insect models to both describe this quantifiable and stereotyped behavior and to manipulate genes and neuron function via numerous genetic and pharmacological tools. This review discusses recent advances in techniques that improve our ability to identify, manipulate, visualize, and compare the genes, neurons, and circuits that are required for the output of this complex and clinically relevant social behavior.