New teeth have been grown from human wee, according to a team of scientists in China!
Urine was used to make stem cells - special 'building blocks' that can grow into any type of cell.
These stem cells were combined with cells from mouse teeth - and then transplanted into mice.
After three weeks they started to look like 'teeth' - but they were not as hard as natural teeth. It's hoped this could be a way of replacing lost teeth.
But other scientists aren't so sure about this method.
Urine is a bad starting point, according to stem cell scientist Professor Chris Mason at University College London.
He said: "It is probably one of the worst sources, there are very few cells in the first place and the efficiency of turning them into stem cells is very low."