Io was the daughter of Inachus, the river god. She was a mortal, and a virgin priestess of Hera, however Hera's husband Zeus made her his lover. Some versions of the myth say that to avoid Hera's jealousy, Zeus transformed Io into a beautiful heifer, but Hera discovered it and made a gadfly keep the animal moving. Zeus eventually restored her human form and made her his lover on a cloud over Egypt. Hera, though, forgave Io for this.