After a childhood of abuse and abandonment, Aileen Wuornos went on a killing rampage that made her America's most infamous female serial killer.

Inside the Aktion T4 program, the little-known Nazi euthanasia initiative that killed as many as 300,000 disabled people.

Neanderthals lived from about 400,000 to 40,000 years ago before they were replaced by modern human ancestors. People today can still have Neanderthal in their genes.

Some are convinced the government uses Area 51 to dissect aliens and study flying saucers. In truth, the classified site has been used to build spy planes — and dump toxic waste.

The Ustaše brutalized and massacred upwards of 300,000 Serbians, 30,000 Jews, and 29,000 Gypsies throughout their four-year reign of terror in Croatia.

After 10 years behind bars, John Dillinger went on a year-long bank-robbing spree that captured America's imagination.

He participated in an infamous massacre of Union soldiers, but when he got to write his own story, Jesse James cast himself as the Robin Hood of the Wild West.

Some hailed Butch Cassidy as a Robin Hood figure for stealing cattle from big ranches that put smaller businesses out of work.

Billy the Kid packed more into his 21 years than most outlaws do into a lifetime.

The Roswell incident is the most famous event in extraterrestrial lore. But, there's more to the story than government conspiracies and flying saucers.

These facts about the Leaning Tower of Pisa reveal everything there is to know about the world's most famous architectural mistake.