Scientists in Japan say they've been able to grow brand new teeth in mice in spots where their old teeth used to be.
Researchers from the University of Tokyo hope that their work will in the future make it possible to grow new teeth and even organs for people too.
The experts put cells containing all the information for building a tooth into the jawbones of mice.
These cells then grew into new teeth that were just as strong as those that come through naturally.
They added a green colour to the cells so they could be sure the mice didn't grow replacement teeth on their own.
The scientists also found that the new teeth grew with nerve fibres inside, so reacted to pain.