Being one of the strongest muscles in the human body, the tongue has another interesting quality. Just like fingerprints, humans also possess unique tongue prints.
The tongue is a unique organ that can be stuck out of mouth for inspection and yet it is otherwise well protected in the mouth and is difficult to forge. All those tiny bumps and ridges on your tongue make it unique from any other due to the different distribution of size and shape, just like your fingerprints. The tongue also presents both geometric shape information which are potentially useful in identity verification applications.
Just like the tongue, each person's set of teeth is also unique, much like fingerprints. Even identical twins do not have exactly the same set of teeth.