The prevalence of childhood and adolescence obesity is increasing to alarming proportions worldwide and poses a major public health problem by significantly elevating the risks of chronic diseases. There is strong evidence that childhood overweight and obesity are risk factors for severe obesity over the whole life course. In fact, longitudinal studies have found that most overweight/obese children would become overweight and obese adults. There is a lack of coupling in the scientific literature between adipose tissue development and biology to obesity prevention and treatment strategies. This is of utmost importance, especially regarding childhood and adolescence, as the major scientific paradigm in studies of adiposity is that the major number of adipocytes is set for life at this early age. This review discusses the current adipose cell biology paradigms to pinpoint the critical factors and periods in childhood overweight and obesity and, consecutively, to develop relevant prevention strategies.