A Shi'ite cleric holds a turban at al-sayed al-Yazdi school run by al-Hawza al-Ilmiyya in Najaf. This year, around 200 fully fledged clerics will graduate, completing a process that requires at least ten years of study. In the Najaf school, a typical day will see clerics in flowing black robes and white turbans giving lectures to groups of students sitting on the floor of a great hall, lined with pointed arches and elaborate mosaics.

A Shi'ite cleric takes off his shoes as he enters Ibn al-Fahd al-Heli school run by al-Hawza al-Ilmiyya in Kerbala.

A Shi'ite cleric reads a book at a library in Najaf, south of Baghdad.

Shi'ite clerics walk outside the Imam Hussein and Imam Abbas shrines in Kerbala. The Kerbala school teaches around 250 students each year, and in Najaf there are more than 1000. Together they are served by a faculty of around 90 teachers.

Shi'ite clerics study at al-Gharawiya school run by al-Hawza al-Ilmiyya in Najaf.

A Shi'ite cleric buys vegetables at a market in Najaf, south of Baghdad.

A Shi'ite cleric (L) speaks to a student at Ibn al-Fahd al-Heli school run by al-Hawza al-Ilmiyya in Kerbala. Students are given instruction in subjects including Islamic jurisprudence, philosophy, theology, logic and interpreting Islam's holy book, the Koran.

A Shi'ite cleric makes his call to prayer at Sadiq Hussaini Shirazi's office who is a top Shi'ite cleric in Kerbala.

Shi'ite clerics study at al-Gharawiya school run by al-Hawza al-Ilmiyya in Najaf.

Shi'ite clerics talk at al-sayed al-Yazdi school run by al-Hawza al-Ilmiyya in Najaf, Iraq. For more than 1,000 years, the al-Hawza al-Ilmiyya in southern Baghdad has been giving religious instructions to thousands of Shi'ite Muslims to help them become clerics.

A Shi'ite cleric holds a turban at al-sayed al-Yazdi school run by al-Hawza al-Ilmiyya in Najaf.

Abdul Hussain Jassim Al Aboudi, 60, a student at al-Gharawiya school run by al-Hawza al-Ilmiyya, holds a book, in Najaf. Shi'ites, who are the majority in Iraq, were repressed under dictator Saddam Hussein, a Sunni Muslim, but now lead the Iraqi government since Saddam was overthrown in 2003. Clerics trained at the Hawza have wide social and political influence, both inside Iraq and abroad.

Shi'ite clerics pray at Sadiq Hussaini Shirazi's office who is a top Shi'ite cleric in Kerbala.

Star Jaber Al-Busaisi (C), 58, a teacher at Ibn al-Fahd al-Heli school run by al-Hawza al-Ilmiyya, speaks to the principal of the school, in Kerbala.

Mohamed Hassan Abdel Hadi Baqer, 25, a student at Ibn al-Fahd al-Heli school run by al-Hawza al-Ilmiyya, looks into a fridge at his home in Kerbala.

A tailor checks the size of a Shi'ite cleric's clothes in Najaf, south of Baghdad.

Students are seen at Ibn al-Fahd al-Heli school run by al-Hawza al-Ilmiyya in Kerbala.