Understanding the role and importance of nutrition in early postnatal life, as an influence on lifelong vulnerability to poor health, is an important part of current research. We need to be able to define optimal patterns of infant feeding, not just to support growth and development in infancy, but also as determinants of later health. To date, much of the focus on the long-term effects of infant nutrition has been on milk feeding, to compare breast and formula feeding and to evaluate the effects of exclusivity, timing and duration of feeding different types of milk in infancy; other aspects of infant feeding such as age at introduction of solid foods and type of weaning diet have received less attention, and relatively little is known about their links to later health. Contemporary data are needed to enable us to move beyond explanation of historical infant feeding data in order to understand and predict health outcomes in future generations. Ongoing and new population studies, that include infants from diverse settings, will be key to providing generalizable data that can be used to define optimal feeding practice. There are some methodological challenges ahead, although significant progress has already been made, and further progress is envisaged in the future. In particular, the opportunity to bring together epidemiological studies and new mechanistic insights that will help identify key aspects of infant nutrition and their causal effects offer great promise both in moving this field forward as well as the potential for health benefits for future generations.