Nonalcoholic steatohepatitis (NASH) is now recognised as an increasing clinical problem in children. Steatosis without significant liver cell injury or fibrosis is the most common form of nonalcoholic fatty liver disease (NAFLD) in both adults and children. Studies in the adult population have variably suggested that steatosis is a benign nonprogressive condition and NASH is recognised as a potentially serious condition with significantly risk of morbidity and mortality. A growing body of evidence suggests that children with NASH frequently show histopathological features that differ from those of adults. The prevalence of this pattern in a wide range of paediatric cases as well as other histopathological lesions and their relevance and prognostic significance in children with NAFLD remains to be determined. Thus the investigators would like to conduct a study of biopsies and clinical information to document the histological features of paediatric NAFLD, to explore the natural history of paediatric NAFLD, and to determine the frequency and prognostic value of these features.