Animals possess a rich repertoire of behaviors, each generated by the orchestrated activity of assemblies of neurons. Neuromodulators, and particularly monoamines, have been found to play a role in the recruitment of such assemblies. The role of specific monoamines in the modulation of behavior has been particularly well studied using invertebrate animals as models. In these animals, the neuronal assemblies underlying a behavior often consist of fewer neurons than those in vertebrates, and in many cases the activity of specific neurons can be causally linked to the expression of a specific behavior. In this overview, we illustrate the concept of chemical orchestration of behavior, using well-studied models of how monoamines modulate complex and long-lasting behaviors in invertebrate animals.