The Aztec 52-year calendar cycle was marked by the New Fire ceremony — a terrifying time when the world might end.

The human liver can regenerate lost tissue.

Fact #123 · Human Body

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

Fact #1129 · Human Body

The gulper eel has a large mouth that allows it to swallow prey bigger than its body.

Fact #1386 · Human Body

A narwhal’s tusk is actually an elongated tooth.

Fact #551 · Human Body

The human eye can adapt to low-light conditions.

Fact #279 · Human Body

Fossils form when organisms are preserved in sediment over millions of years.

Fact #678 · Human Body

The Earth is about 4.5 billion years old.

Fact #172 · Human Body

The Sumerians developed one of the earliest known writing systems.

Fact #644 · Human Body