Actual physical, technical and psychological potential of the athletes is formed from inborn abilities in the process of multi-year training (MYT). It is commonly presumed, that being properly organised and conducted MYT may be used as a powerful and purposeful modifier of natural growth and development. MYT is aimed to: - provide an optimal physical and functional development of juvenile athletes until the age of full biological maturity; - form a specific body build and composition matching to requirements of a chosen sport; - develop specific structure of sport abilities prior the optimal age of top performance; and - develop specific competitive skills and variety of training skills. MYT has as time borders three age landmarks: average optimal age of the beginning of sport training in chosen sport, average age of first national success and average age of top performance. - Factors which determine outcome of MYT are: genetic program of individual development (individual physical and learning abilities, individual reserve of adaptation), physical and psychological workloads, training methods and regimens, skill learning and training, hormonal modulation via physical training influences. The objectives of this project were: - to scrutinize and define key concepts and terms employed to describe the phenomena of growth and development; - generalize basic knowledge of contemporary theories and principles of through the late childhood, adolescence and youth; - suggest an interpretation of individual growth and development within conceptual framework. To achieve objectives we used analysis of - periodization of human growth and development; - the role of motor-visceral reflexes; - theory of functional systems and system-genesis; - theory of sensitive periods in motor leaning and physical development; - concept of hormonal scissors. Conclusion: MYT in swimming affects the growth and produces specific adaptations that benefit performance in the sport. Within individual genetic limits it can modify significantly the output of the growth and develop a highly specific structure of abilities and specific performing skills to their full potential. The process of the grooming of the future champions overlaps on pre-adolescent and adolescent periods of individual development (including puberty) and lasts up to full biological maturity. It is important to consider general principles of growth and development as well as gender and individual differences in growth patterns and velocity and in maturity when planning training. MYT should be sub-divided into stages in accordance with particularities of biological growth and development. Each stage will target its own specific objectives. Lower stages of MYT are aimed to build aerobic functional foundation and basic sport skills, assist to the health improvement and develop in young athletes an interest and commitment to the sport. Higher stages of MYT are aimed to develop specific abilities and functions, limiting the level of achievements in elite athletes, create a strong and stabile sport motivation, develop specialized technical skills to the highest level of perfection.