Unicorns are incredibly potent magical creatures whose horns pack a lot of healing and transformative power. Meanwhile, gray goo is the nightmare scenario for nanotechnology, in which nanotech runs wild forever, turning all organic matter into more of itself. But if these two amazing phenomena collided, which one of them would win?
You decide, in our poll below. This could be the fate of the world you're deciding, so think carefully:
Top image: Artist unknown.