Dr. O.TAR NORWOOD, an American dermatologist, has classified hereditary baldness in males into 7 types according to the severity known as NORWOOD CLASSIFICATION OF MALE PATTERN BALDNESS (MPB)

Dr. Norwood's classification was introduced in 1975 and has been the most popular among hair transplant physicians and has been used until this day. 

To better understand all these 7 types of MPB, we have regroup them into the following 4 major categories: