The Theogony Of Hesiod is a poem describing the origins and genealogies of the Greek gods, composed circa 700 BC. Although it is often used as a sourcebook for Greek mythology, the Theogony is both more and less than that. In formal terms it is a hymn invoking Zeus and the Muses: parallel passages between it and the much shorter Homeric Hymn to the Muses make it clear that the Theogony developed out of a tradition of hymnic preludes with which an ancient Greek rhapsode would begin his performance at poetic competitions. It is necessary to see the Theogony not as the definitive source of Greek mythology, but rather as a snapshot of a dynamic tradition that happened to crystallize when Hesiod formulated the myths he knew—and to remember that the traditions have continued evolving since that time.