The body is like a car motor. We burn fuel (sugar) mixed with oxygen to create energy. And just like a motor -- we get hot.
Your body is hotter deep in its core, near the heart. One of the benefits of your heart pushing blood around is to distribute that heat throughout your whole body.
As you might imagine, the further blood gets from the heart the cooler it gets. That's why your hands, toes and nose always seem to get cold first -- they're not as hot-blooded as the rest of you.
When the environment gets really cold, like a blizzard in northwest China in 2006 that dropped to 45 degrees below zero, it's those areas far from the heart that are the hardest hit. Frostbite is much more common where blood doesn't flow as fast or as hot.
Have a frostbite picture you'd like to share? Tell us about your experience, see other readers' frostbite injuries and submit your own frostbite picture.