The Generation R Study is a population-based prospective cohort study from fetal life until adulthood. The study is designed to identify early environmental and genetic pathways leading to normal and abnormal growth, development and health. An important focus of Generation R is to identify early life determinants of common (mostly non-communicable) diseases in adulthood. Pregnant women living in the Rotterdam area, the Netherlands, were included between 2002 and 2006. After birth, the children and their parents have been followed in multiple assessment waves up until young adulthood.