Answer:
The man who invented it doesn't want it. The man who bought it doesn't need it. The man who needs it doesn't know it. What is it?
A girl was ten on her last birthday, and will be twelve on her next birthday. How is this possible?
It cannot be seen, cannot be felt, Cannot be heard, cannot be smelt. It lies behind stars and under hills And empty holes it fills. It comes first and follows after, Ends life, kills laughter.
I cost no money to use, or conscious effort to take part of. And as far as you can see, there is nothing to me. But without me, you are dead.
When they are caught, they are thrown away. When they escape, you itch all day.
You use it between your head and your toes, the more it works the thinner it grows.