Generation R is a prospective, population based cohort study from fetal life until young adulthood in a multi-ethnic urban population in Rotterdam, the Netherlands. The study is designed to identify early environmental and genetic causes of normal and abnormal growth, development and health. Eventually, results forthcoming from the Generation R Study have to contribute to the development of strategies for optimizing health and healthcare for pregnant women and children. Generation R is a prospective, population based cohort study from fetal life until young adulthood in a multi-ethnic urban population in Rotterdam, the Netherlands. The study is designed to identify early environmental and genetic causes of normal and abnormal growth, development and health. Eventually, results forthcoming from the Generation R Study have to contribute to the development of strategies for optimizing health and healthcare for pregnant women and children.