The frigatebird can stay aloft for weeks — sleeping on the wing for seconds at a time using half its brain.

Stress hormones prepare the body for a fight-or-flight response.

Fact #959 · Human Body

Fingernails grow faster than toenails.

Fact #110 · Human Body

The Thirty Years’ War affected much of Central Europe.

Fact #1171 · Human Body

Some animals sleep for years.

Fact #1720 · Human Body

The Tyrannosaurus rex may have had excellent vision.

Fact #687 · Human Body

The Earth is not perfectly round.

Fact #1719 · Human Body

The first artificial heart was implanted in the 1980s.

Fact #1209 · Human Body

The Earth's mantle lies between the crust and core.

Fact #301 · Human Body