And we'll talk more about Ali in a little bit. But the general division is over who should succeed Muhammad after his death as the leader of the Muslim community. Shias believe it should be members of Muhammad's family and especially descendants of Muhammad, while the Sunnis believe that it doesn't necessarily have to be that. But as we'll see, this division becomes stronger and stronger and stronger as there's more and more bloodshed between the two parties. Because so much of this revolves around the family of Muhammad, let's just review that first and then we'll talk about the division over who should succeed Muhammad as caliph or successor to lead the Muslim community. So you see Muhammad right over here, born 570. We have his birth on our timeline as well.