The story, one of the oldest, if not the oldest in the world, concerns the birth of the gods and the creation of the universe and human beings. In the beginning there was only undifferentiated water swirling in chaos. Out of this swirl, the waters divided into sweet, fresh water, known as the god Apsu, and salty bitter water, the goddess Tiamat. Once differentiated, the union of these two entities gave birth to the younger gods.