Hussaini, also known as the Aga Khan, died on Tuesday, February 4, aged 88. A colossally wealthy philanthropist, he was also the imam of the Nizari Ismaili faith, an esoteric branch of Shia Islam that changed the history of the Middle East.

Rahim Al-Hussaini was named Wednesday as the new Aga Khan, spiritual leader of the world's millions of Ismaili Muslims. The 53-year-old succeeds his father, who died on Tuesday.

Hussaini, son of Prince Karim Al-Hussaini Aga Khan IV, has been named in his father’s will as his successor to lead the Nizari Ismailis, a Shia Muslim denomination. We take a look at this branch of Shia Islam that has 15 million members worldwide.