Milk, the first and for a time only source of nutrition for mammals, influences early growth and development and may provide a foundation for health throughout the entire lifespan. It is therefore mandatory that milk substitutes have a composition which fulfills the same goals and confers as close as possible the overall health benefits of human milk. Moreover, in many populations, milk continues to play a major role in a healthy and balanced diet throughout life: During childhood, pregnancy and adulthood, intake of cow’s milk has important beneficial effects on linear growth, bone development and the risk of developing caries, and it is important in the prevention and treatment of undernutrition in low-income countries. This publication contains the presentations and discussions of the Nestlé Nutrition Institute Workshop held in Marrakech in March 2010. It focuses on three main topics: milk during pregnancy and infancy, milk during childhood in low- and high-income countries, and general aspects of milk in adult nutrition. Together, these contributions cover most aspects of milk during the life cycle in a global perspective, making the publication a comprehensive textbook.