Nonalcoholic fatty liver disease (NAFLD) is a liver condition characterized by excess fat accumulation in hepatocytes, often accompanied by inflammation and hepatocyte injury (nonalcoholic steatohepatitis, NASH). NAFLD is closely associated with insulin resistance, obesity, and metabolic syndrome, affecting 10-40% of adults worldwide and being the most common liver disease in children and adolescents in developed countries. The disease progression can lead to cirrhosis and hepatocellular carcinoma (HCC). Genetic and epigenetic factors contribute to the variability in disease phenotype, severity, and progression. Current management options include lifestyle changes, dietary alterations, and bariatric surgery, but no effective medical interventions exist. Diagnosis primarily relies on liver biopsy, with non-invasive methods being developed for follow-up monitoring. The article discusses the epidemiology, pathophysiology, genetics, epigenetics, and diagnostic approaches to NAFLD.Nonalcoholic fatty liver disease (NAFLD) is a liver condition characterized by excess fat accumulation in hepatocytes, often accompanied by inflammation and hepatocyte injury (nonalcoholic steatohepatitis, NASH). NAFLD is closely associated with insulin resistance, obesity, and metabolic syndrome, affecting 10-40% of adults worldwide and being the most common liver disease in children and adolescents in developed countries. The disease progression can lead to cirrhosis and hepatocellular carcinoma (HCC). Genetic and epigenetic factors contribute to the variability in disease phenotype, severity, and progression. Current management options include lifestyle changes, dietary alterations, and bariatric surgery, but no effective medical interventions exist. Diagnosis primarily relies on liver biopsy, with non-invasive methods being developed for follow-up monitoring. The article discusses the epidemiology, pathophysiology, genetics, epigenetics, and diagnostic approaches to NAFLD.