The first two years of life are a period of unparalleled growth and change. Within a state-of-the-art biopsychosocial framework, this innovative volume explores the multiple contexts of infant development—the ways in which genes, neurobiology, behavior, and environment interact and shape each other over time. Methods for disentangling, measuring, and analyzing complex, nonlinear developmental processes are presented. Contributors explore influences on the infant's growth in major domains, including cognitive and socioemotional functioning and mental health. The consequences of family stress, poverty, and other adversities are probed, and promising directions for prevention and intervention identified.