This review focuses on important observations regarding infant health around 1900 when breastfeeding was not considered a matter of importance. The discovery of lactobacilli and bifidobacteria and their relevance for health and disease was an important milestone leading to a decrease in infant mortality in the first year of life. At the same time, pediatricians realized that the fecal composition of breast-fed and bottle-fed infants differed. Observations indicated that this difference is linked to milk composition, particularly due to the milk carbohydrate fraction. Circa 1930, a human milk carbohydrate fraction called gynolactose was identified. This was the starting point of research on human milk oligosaccharides (HMO). In the following years, the first HMO were identified and their functions investigated. Studies after 1950 focused on the identification of various HMO as the bifidus factor in human milk. In the following 30 years, a tremendous amount of research was done with regard to the characterization of individual HMO and HMO patterns in milk. In this short introduction to the history of HMO research, which ends circa 1980, some outstanding scientists in pediatrics and chemistry and their pioneering contributions to research in the field of HMO are presented.