Introduction : first steps to optimal health and fitness throughout life -- Theoretical considerations : what can we learn from the natural and experimental models? -- Nutrition of pregnant mothers and their children in early life : human studies -- Growth and somatic development of preschool children -- Nutritional status and dietary intake in early life -- Functional development and physical activity during early childhood -- Influence of varying nutrition and environment on somatic development and physical fitness -- Development of obesity and its influence on the functional capacity of children and youth -- Influence of environmental factors -- Influence of motor stimulation, physical education, and spontaneous physical activity -- Criteria for the evaluation of morphological and functional development in preschool children : recommendations -- Summary of experimental results -- Perspectives : physical activity, early prevention of diseases, and development of positive health.