This was a women’s festival of Demeter (‘barley mother’) the Greek goddess of agriculture, health, birth and marriage. She was associated with the Roman goddess Ceres; she was also the daughter of Cronos and Rhea, and therefore the sister of Zeus. Her priestesses were addressed with the title Melissa. Today was the first day, the Stenia. The Stenia are said by Photius to have celebrated the return of Demeter from the lower world (Anodos), and the women railed at each other by night. Some of the features of this three-day festival are identical with those of harvest festivals long observed in the north of Europe.
The cult was practised universally in the Greek world, from the Black Sea to Lesbos, but the secrets of the rites were so well kept that even today we know very little of what the women did. It is believed that the participants dressed in fawn skins and, carrying a thyrsus, a rod topped with ivy, wandered the mountains at night, participating in such ritualistic activities as nursing baby wild animals and consuming milk, wine and honey. The women would imitate the Bacchae (Maenads), performing frenzied, ecstatic dances, sometimes around an image of Dionysus. On the first day, women gathered in the temple area. On the second day there was fasting, and they would return home for the night.
The rites included married women, this being their only opportunity all year to get away from their husbands and families. Grain was burnt as an offering to Demeter. Piglets, sheep and goats were sacrificed. After the Thesmophoria ended, the priests would gather up the large numbers of female figurines that had been usd in the rituals, and bury them. Unlike the Mysteries of Dionysus, the Thesmophoria seems to have been revered by the men of Athens, but is mocked in Aristophanes's Thesmophoriazusae.