Human milk provides the optimal nutrition for new-borns, as it produces nutrient patterns adapted to their physiological requirements. At the same time, the functionality of the new-born immune system is immature and it has been demonstrated that nutrition during the postnatal period determines its development. This project is focused on understanding the bioactive components of human milk and on classifying them according to their beneficial activity on the new-born immune system. Five groups of compounds have been considered: 1) antimicrobial, 2) promoting immune system development, 3) tolerogen, 4) anti-inflammatory, and 5) probiotic. Recent advances in understanding of the composition of human milk have paved the way for the production of infant formulas increasingly suitable to infants. This project has furthered the study of clinical trials as well as the consequent benefits of the addition of oligosaccharides to infant formulas intended for babies.