Demeter is the goddess of the harvest and a daughter of Cronos and Rhea.
Demeter had one child by Poseidon, who had raped her. This child was Persephone, goddess of flowers; Demeter later thought it was a good thing that she had such an adorable daughter. But one day, Persephone was playing with her friends when Hades came out of the ground and abducted her to be his queen. Demeter went on strike for a year, refusing to make the crops grow. During this time, she asked everyone on earth where Persephone was. Nobody knew her whereabouts - except for Helios, the sun. Helios told Demeter what happened, Demeter told Zeus, and Zeus told Hermes, who went to Hades with a petition declaring that Persephone had to come back, provided she hadn't eaten anything down in Hades. She had eaten something, unfortunately: six pomegranate seeds. So Zeus said Persephone had to stay with Hades six months of the year, during which time Demeter mourned. As a result, fall and winter now occur due to Demeter's near-lack of activity during those six months.