The composition of breast milk provides guidance for the composition of infant formula but infant formula also should be evaluated based on a comparison of outcomes in exclusively breast-fed and formula-fed infants. A balanced gut microbiota is crucial for health. Conversely, an altered gut microbiota composition and/or activity (dysbiosis) contributes to diseases. In formula-fed infants, early nutritional interventions targeting the gut microbiota by using probiotics and/or prebiotics or more recently, postbiotics and selected human milk oligosaccharides have the potential to prevent diseases. During this presentation Professor Hania Szajewska summarizes optional ingredients included in infant formulas and their health-related outcomes. Special focus will be on interventions aimed at modifying the gut microbiota