Hades locked Persephone in a beautifully decorated room in the Hall of Hades, but Persephone refused to eat. She had heard if you ate anything in Hades, you could never leave. Finally, in desperate hunger, Persephone ate six pomegranate seeds; meanwhile, back on earth, Demeter, missed her daughter terribly and the crops were dying. It was clear this could not go on, so Zeus sent his son Hermes to work a deal with Hades. This was the deal Hermes worked out:
To the ancient Greeks, that was the reason for seasons - winter, spring, summer, fall.