By the time our children reach kindergarten their learning and developmental patterns are already taking shape, as is a trajectory for their future health. Now, for the first time, scientists have amassed a large collection of research that looks "under the skin", to examine how and why experiences interact with biology starting before birth to affect a life course. The implications of the research are far reaching, from new approaches to learning and language acquisition, to new considerations for the health effects of social environments affecting large populations, and policies for early childhood care and education.