Obesity develops already in infancy and adolescence. The researchers of this study expect that modifications in adipose tissue and the biology of fat cells already take place in infancy. These modifications affect the development of obesity and its associated diseases. The scientists here examine the development and changes of adipose tissue biology and function and the hormone production of the fat cells in relation to the age and physical development of children. The results in normal weight and obese children will be compared and changes in the adipose tissue that are connected with early emergence of obesity in children will be identified. Necessary for this study is an enormous bio database of adipose tissue probes of children which exists at the University Hospital.