What is something unseen (or invisible) that you wish you could see?

Ever since I learned that bees can see ultraviolet light, I have thought about what it would be like to see more frequencies in the electromagnetic spectrum than what we call "visible light."

I suppose many of the objects that we call "black" (reflecting no visible light) would appear to have different colors. "Oh, that one looks ultra-violet, that one looks x-ray, and that one looks black."