Maternal diet, nutritional status during pregnancy, and the early diet of the offspring play an important role in later health. The short- and long-term outcomes of early nutrition have been extensively studied in recent decades. One of the most commonly investigated nutritional interventions is breastfeeding, which is associated with a number of positive short- and long-term outcomes. A short-term effect of breastfeeding is reduced morbidity and mortality in children from poor living conditions and in preterm infants. Breastfeeding is associated with better cognitive development and also has a long-term protective effect on obesity risk, prevalence of type 2 diabetes, and a lowering effect on blood pressure. Selected nutrients have undergone extensive investigation to show their role in disease prevention or improved development, e.g. protein intake in infancy seems to be associated with a later risk of obesity or docosahexaenoic acid supplementation has a positive impact on cognitive function. Another consideration is the fast catch-up growth in small for gestational age infants as an important factor associated with adult risk of cardiovascular problems. On the other hand, high protein and energy intake seems to be positively associated with some indicators of cognitive development. Most of the evidence comes from observational studies that cannot exclude potential confounders. Animal studies demonstrate causality but should not be directly extrapolated to humans. The number of randomized controlled studies is increasing but long-term follow-ups are necessary to obtain convincing results. The majority of these trials compare different infant formula compositions and macro- or micronutrient supplementation. One of the major questions is to define a critical (or opportunity) window and a mechanism of nutritional influence on several health outcomes.