We are interested in how the brain performs complex cognitive tasks and how groups of neurons function together to generate behaviors. The human brain is comprised of billions of neurons with trillions of connections between them, making it one of the most complex biological systems. To understand the processes underlying cognition, we use the brain of the fruit fly, Drosophila melanogaster as a model system. Fruit flies are an ideal preparation to study such questions because (1) their brains possess far fewer neurons than our own brains, (2) they perform many of the same cognitive tasks that even we do, and (3) their nervous system can easily be manipulated using a variety of genetic tools. Specifically, we focus on two major questions: (1) How do flies process multisensory cues in the process of deciding to mate? (2) How are aggression and aggressive behaviors represented in the Drosophila brain?