How micromotives, the microstructural features of interactions, and macrobehavior are related is a fundamental question in all social sciences. In this article we argue that laboratory experiments are a useful tool to study this question, because the experimenter can measure motivations, manipulate microstructures, and sometimes even exploit variation in the macrosocial environment. We illustrate the experimental approach with the help of four examples from the context of voluntary cooperation. The examples (from previous and new experiments) illustrate the link between individual pro-social motives and wage formation in labor markets, the inevitability of the 'Tragedy of the Commons,'' and two potential ways to avoid the tragedy: sorting and punishment.