Human milk oligosaccharides (HMOs), also known as human milk glycans, are short polymers of simple sugars that can be found in high concentrations in human breast milk. Human milk oligosaccharides promote the development of the immune system, can reduce the risk of pathogen infections and improve brain development and cognition. The HMO profile of human breast milk shapes the gut microbiota of the infant by selectively stimulating bifidobacteria and other bacteria.