The liver is the largest and most complex organ in the human body. It is located in the upper right part of the abdominal cavity. The liver is an organ with a number of vitally important functions and it plays a role in the detoxification of the organism. Everyday, humans are exposed to various xenobiotics which are found in the air, soil, water, plants and animals. The term xenobiotic means any substance that is "foreign" to the body. Xenobiotics are also present in the food we consume every day in the form of preservatives. Preservatives slow down the biological and chemical decomposition of food and thus extend its shelf life. Detoxification is a process in which xenobiotics are metabolized in an organism and ultimately excreted from it. The liver plays a key role in this process. The basic principle of detoxification includes Phase I and Phase II reactions which take place in the liver parenchyma. Oxidation, reduction and hydrolysis processes belong to the Phase I reactions. Most Phase I reactions are catalyzed by the cytochrome P-450 enzyme monooxygenase system. Phase II reactions include the conjugation process which is a process in where a molecule foreign to the body combines with endogenous molecules with the aim of acquiring solubility in water, which ultimately enables more efficient excretion from the body. Phase II reaction enzymes catalyze the addition of functional groups such as acetate, sulfate, or glucuronate to xenobiotic metabolites.