Art History Abridged: 

Jupiter is one righteous manwhore, who falls in love with an earthwoman, Io. However, naturally, his wife Juno is less than pleased about his many affairs, so he has to hide when seducing, and inevitably, making love to Io. So Jupiter hides in the wind and Io makes love to the air, and then to protect her from Juno’s wrath: Jupiter turns Io into a heifer.  

(Correggio’s Jupiter and Io)