Bacteria are prevalent in the human gut as part of the gut microbiome. Most have a benign effect; however some may cause disorder and others are positive for our health. Human milk oligosaccharides (HMOs) are uniquely found in human milk and represent the third largest component. HMO are thought to confer some of the health benefits associated with breast feeding including the development of improved gut microbiota, reducing infection, improving immune function, possible role in promoting brain development. Emerging science also supports a role in growth and metabolism.