A city state is a city that also considers itself a state that has its own political organization, its own way of functioning. It's not dependent on any other government forms, and it's analogous to what we see in classical Greece, where you have the city states of Athens and Sparta. Now, what's particularly interesting is what's going on around Lake Texcoco in the 14th century. In 1325, you have the city of Tenochtitlan form on this island in Lake Texcoco, and initially, Tenochtitlan is one of the weaker city states around Lake Texcoco. You see many of these city states, some of the stronger ones, you have Texcoco right here, and in particular, you have Azcapotzalco. But as we fast forward roughly 100 years, you get to a situation where Azcapotzalco falls into a civil war. Their ruler dies, and there's a succession battle, and the various city states around Lake Texcoco take sides.