Imam Mahdi is the eleventh Imam’s son. He was called after The Holy Prophet (SW) and was born in 256 or 255 AH (anno Hijra) in Samera. He was dependent upon his father (till 260 A.H.). Imam Mahdi was unseen from the eyes of common people and nobody could see him except special group of Shi’ites could not deserve his meeting.
After the martyrdom of his father (Imam Hassan-e Askari [Pbuh]) he was appointed as the next Imam. Then he was hidden by God’s command and he was just observable by the special deputies of his own.