Pan frying is a form of frying characterized by the use of minimal cooking oil or fat (compared to shallow frying or deep frying); typically using just enough oil to lubricate the pan. In the case of a greasy food such as bacon, no oil or fats may be needed. As a form of frying, pan frying relies on oil as the heat transfer medium and on correct temperature and time to retain the moisture in the food. Because of the partial coverage, the food must be flipped at least once to cook both sides.