A wisdom tooth is one of the four large molars that grow at the very back of your mouth, usually appearing when you're between 17 and 25 years old. They're called wisdom teeth because they arrive much later than your other teeth, supposedly when you're older and wiser.

These teeth were useful to our ancient ancestors, who needed extra grinding power for tough foods like raw plants, roots, and meat. But modern humans have smaller jaws than our ancestors did, which means there's often not enough room for wisdom teeth to fit properly. When they try to push through, they can grow in crooked, get stuck under the gum, or crowd the other teeth.

Because of these problems, many people have their wisdom teeth removed by a dentist or oral surgeon. The procedure is common and usually goes smoothly, though your cheeks might be puffy for a few days afterward. Some lucky people never develop wisdom teeth at all, or have enough room for them to grow in without causing trouble. Scientists think wisdom teeth might eventually disappear from humans entirely through evolution, since we don't really need them anymore for the softer foods we eat today.