The Growth, Exercise and Nutrition Epidemiological Study in preSchoolers (GENESIS) study is a large-scale epidemiological study conducted in Greece, attempting to assess growth, development and nutritional status of preschool children. In this study, 1218 males and 1156 females one to five years old, stratified by parental educational level (as determined by the 1999 Census), were examined from 105 nurseries in five counties. Approximately 300 demographic, lifestyle, physical activity, dietary, anthropometrical and DNA variables have been recorded from the study population (children and parents).