The Sentinelese people of North Sentinel Island speak a language completely unknown to the outside world.

About 80% of millionaires are self-made.

Banksy, the anonymous street artist, has never been definitively identified despite decades of speculation.

The Vikings used to give kittens to new brides as essential household gifts.

Beethoven's Fifth Symphony opens with one of the most recognizable motifs in classical music — four notes long.

Islam has five pillars: faith, prayer five times daily, charitable giving, fasting during Ramadan, and pilgrimage to Mecca.

Chocolate was once used as currency by the ancient Aztecs.

Aboriginal Australians have oral traditions and songlines that preserve ecological knowledge going back tens of thousands of years.

In Norse mythology, Odin sacrificed one eye to drink from the Well of Wisdom and gain cosmic knowledge.