Many of the individual nutrients in the human diet have been recognized for hundreds of years. However, identifying the daily requirements for these nutrients and their role in human metabolism and homeostasis are recent developments. Although, historically, the major focus in pediatric nutrition has been growth, attention to the relationship between dietary nutrients and other health outcomes, such as host defense, psychomotor development, and long-term health, has occurred only recently and has led to major advances in our understanding of the importance of nutrition in infancy and childhood. Several of the important advances in our understanding of the role of micronutrients and macronutrients in the health and development of infants and children are described below, along with historically relevant events in the history of infant feeding, childhood nutrition, and public health and fluid therapy. The history of infant feeding and formula development is given special emphasis because in many ways it is synonymous with the early history of the science of pediatric nutrition and also because of its importance in the practice of pediatrics in the past century. Each of the topics discussed in this review could serve as the basis for a full historical review by itself, and because of space limitations, many topics are not even discussed. Thus many, and perhaps most, of the individuals who have contributed in a very important way to the development of our understanding of the science of pediatric nutrition have not been mentioned. For this we apologize.Energy. We have only recently begun to unravel the complex central and peripheral signaling pathways and chemical messengers that govern energy intake and expenditure in healthy and compromised infants and children. The technique of indirect calorimetry pioneered by Voit in the last half of the 19th century and applied to infants by Forster in 1877 [as