Enamel, the outer layer of teeth, is the hardest biological substance — harder than bone.

There are more possible shuffles of a deck of cards than seconds since Earth formed.

Fact #1675 · Human Body

The use of defibrillators can restore normal heart rhythm.

Fact #1227 · Human Body

Practice can strengthen neural pathways in the brain.

Fact #968 · Human Body

The primacy effect describes better recall of early information in a sequence.

Fact #1477 · Human Body

Water is the only natural substance that commonly exists as a solid, liquid, and gas on Earth.

Fact #175 · Human Body

Certain reptiles regulate body temperature through basking.

Fact #527 · Human Body

Ankylosaurs had armored bodies and clubbed tails.

Fact #629 · Human Body

The Trail of Tears forced Native American tribes westward in the 1830s.

Fact #1129 · Human Body