see the dark side of the moon

Etymology
The "far side of the moon", the side we don't see from home, is sometimes referred to colloquially as the "dark side of the moon" where "dark" means "unseen" rather than "unlit." In the latter sense, there is no dark side, as both sides of the moon receive equal sunlight. This makes it more or less impossible to see the "dark" side of the moon if this is taken to mean "unlit", and it is impossible to see the "far" side of the moon from Earth in the sense of "unseen."

Verb

 * 1)  To do or experience something exceedingly difficult or rare.