This is a really gorgeous painting by Jacopo Tintoretto depicting the "Origin of the Milky Way, 1575-1580." Jupiter (Zeus) seeks to give immortality to his son, Hercules, conceived during an illicit affair with a mortal woman Alcmene. He knows that only the breast milk of a goddess can accomplish such a thing and as luck would have it Juno (Hera) is lactating. Jupiter discovers Juno sleeping and attempts to latch the baby to her breast -- thinking she might not notice (really? ) When she wakes and pulls her breast away from the feeding infant, her milk sprays into the heavens and produces the stars. (Click on the image to see a larger version)
Here is a wonderful and incredibly informative little podcast about The Origin of the Milky Way from Karen Allen of the National Gallery in England exploring the wealth of creation myths alluded to in the painting (including the origin of lillies) and lovely details about Tintoretto's artistic storytelling. It's fabulous.