"Human milk oligosaccharides (HMOs) are the third most abundant component of breast milk, but the composition varies greatly between women and changes over the course of lactation, as explained by Prof. Lars Bode. Current research focuses on maternal drivers of HMO composition, HMO effects on short- and long-term infant health and development, as well as on the development of HMO-based therapeutics for people of all ages. HMOs have prebiotic effects, but are more than just ""food for bugs"" as they can also serve as antimicrobials and antiadhesives and, in addition, directly alter epithelial and immune cell responses. Establishing HMO structure-function relationships and developing a deep mechanistic understanding of their mode of action provides an opportunity to develop targeted pre-, pro-, and synbiotics, specifically selecting microbes that thrive on select HMOs while leaving other HMOs intact to be able to exert other, non-prebiotic functions. This content was presented in May 2021 and reflects the best available information about Covid-19 at that time."