Shia Islam is the second largest denomination of the Islamic Faith, after Sunni Islam, having about 15% of Muslims worldwide. Shias adhere to the teachings of Islamic prophet Muhammad, but differ from Sunni in following the religious guidance of his family (who are referred to as the Ahl al-Bayt) or his descendants known as Shi'a Imams, whom they consider to be infallible. A large portion of the world's Shia live in the Middle East, especially Iran, where 90% of the population is Shia. (Information source: Wikipedia)
Territory size shows the proportion of the world's Shia Muslims living there.