"Hey doc, why do my teeth chatter when I'm cold?"

Good question. And the answer is pretty cool.

Your body comes equipped with its own thermostat—part of the brain called the hypothalamus‚ which keeps it set at a constant temperature of 98.6 degrees Fahrenheit.

When it's cold outside and your body temperature starts to drop, the hypothalamus sends a message to your body that it needs to warm up.

One way it does that is through your muscles, which generate heat by shivering. Teeth chattering is just a form of shivering
.
So next time you find yourself chilled and chattering, don't worry. Just thank your body for trying to protect you.