Isis belongs to the older Egyptian deities and according to the Pyramid Texts she is the daughter of Geb and Nut, sister of Set and Nephthis, sister and wife of Osiris.
The myth of Isis and Osiris is narrated by Plutarch and according to Herodotus, who visited Egypt in the fifth century BC, they were the only gods worshipped at the time.
The cult of Isis becomes very popular and spreads to the entire Mediterranean area, Greece included. The trading relations between Athens and Egypt resulted among other things in the importing of the cult of Isis to Piraeus, already in the fourth century BC. Thereafter, Isis is ascribed with faculties belonging to Demeter, is identified with Aphrodite and is Hellenized since her cult is adopted in many Greek regions. Her sanctuary at Marathon by the sea was brought to light in 1968. A ruined part of the enclosure and its monumental propylon, from which the processional way leads to the temple, have been preserved. An intact, colossal Egyptian statue of a young man as well as the lower body of a statue of Isis have been discovered in front of the propylon. The sanctuary was founded in the second century AD. Contemporary with the Iseion is the Roman valaneion (=baths), found to the east of the enclosure.