The contentious nature-nurture debate in developmental psychology is poised to reach a rapprochement with contemporary concepts of gene-environment interaction, transaction, and fit. Discoveries over the past decade have revealed how neither genes nor the environment offers a sufficient window into human development. Rather, the most important discoveries have come from unearthing the manner in which the environment alters gene expression (and how genes impose limits on environmental effects), how biology and the environment influence each other across time, and how maximizing gene-environment fit leads to optimal outcomes for children. The manner in which these factors operate in tandem should direct future scholarship, practice, and public policy.