Hepatic steatosis is an accumulation of fat in the liver. It is an augmentation of fat in the hepatic cells and can cause complications in cases of obesity, alcohol intoxication (due to an excessive consumption of alcohol) or hepatic disorders . Steatosis can be isolated and we call it pure steatosis or it can be associated with hepatitis: Non-Alcohol Steatosis Hepatitis( or NASH).Usually, people suffering from those do not show any symptoms. In some cases, steatosis can evolve into fibrosis that may transform into cirrhosis due to obesity and overweight in our occidental societies. Several mechanisms are involved in the accumulation of intrahepatic fat, including increased flux of fatty acids to the liver, increased de novo lipogenesis, and/or reduced clearance through β-oxidation or very-low-density lipoprotein secretion. This article summarizes the mechanisms involved in the accumulation of triacylglycerols in the liver, the clinical implications, and the prevention of hepatic steatosis, with a focus on the role of mitochondrial function and lifestyle modifications.