Liver biopsy, since 1883, when were first performed, became the gold standard to confirm the earlier stages of fibrosis and grading of non-alcoholic fatty liver disease (NAFLD) and for distinguishing simple steatosis from non- alcoholic steatohepatitis (NASH). General limitations of liver biopsy are sampling error and inter- and intraobserver variability. Also procedure is invasive and that's why associated with some potential adverse effects and complications which may be minor (pain or vagal reactions, transient hypotension) or major such as visceral perforation, bile peritonitis or significant bleeding. Presence of steatosis, hepatocellular injury in the form of ballooning, lobular inflammation and perisinusoidal fibrosis, usually with a zone 3 distribution are considered to be most important histological features of adult NAFLD which may differ from bariatric surgery or pediatric patients. In addition, grading and staging and current semiquantitative systems for NAFLD assessment are discussed.