Demeter, goddess of the harvest, was mother of Persephone who became the wife of Hades after he abducted her.
Whilst searching for Persephone, Demeter came to Eleusis. Disguised as an old woman, she asked the king, Celeus, for shelter. After he agreed she rewarded him by teaching his son Triptolemus the secrets of agriculture. The boy then passed on his knowledge, so humanity learned how to plant, grow and harvest grain.
The sacred mysteries of Demeter are celebrated at the Thesmophoria in October (for married women) and during the Eleusinian Mysteries. At the Thesmophoria we fast and eat only pomegranate seeds for two days before sacrificing pigs on the third day. I cannot tell you about the Eleusinian Mysteries, but one day you may learn. Remember that the Homeric Hymn to Demeter tells of the day of Persephone’s return at the very beginning of bountiful springtime.