The study of brain development and that of behavioral development have historically proceeded independently of one another. This is an unfortunate set of circumstances, given that the disciplines concerned with development—for example, developmental psychology, pediatrics, psychiatry, clinical psychology, and the neurosciences—have much to learn from each other. Drawing on recent advances in the developmental brain and behavioral sciences, we illustrate the transdisciplinary approach our group has adopted in the service of uniting the research on brain and behavior in the context of development. We specifically report on our nonhuman primate and human studies that collectively illustrate our “genes to behavior” approach to the study of development. Our goal in summarizing our research in this fashion is to promote discussion about promising templates for how research on brain, behavior, and development might proceed into the 21st century.