The world is full of things you didn't know, things you thought you knew, and things you never knew you never knew. That's where Your Brain On Facts comes in. It explains surprising science in simple language and pushes back against historical inaccuracies (and flat-out myths) taught in history class. It gives you the unexpected origins of pop culture classics, and generally fills the minds of readers with "bonus facts" to add to any conversation.

For example:

During WWII, an American dentist convinced the military to test incendiary bomb dispersal by Mexican free-tailed bats. His plan, Project X-ray, was to drop bats strapped with tiny incendiary bombs over Japanese cities, to roost in eaves and attics. When the bombs exploded simultaneously, there would be too many fires to put out. Two branches of the service and the equivalent of $35 million later, it was cancelled in favor of the Manhattan Project. ​

An American unit was pinned down at Chosin Resevoir during the Korean conflict. They called for "tootsie rolls," code for a resupply of mortar rounds. They received actual Tootsie Rolls. The candy was a godsend because they were low on food, and the freezing conditions meant the candy could be used to patch holes in vehicles and equipment. The men dubbed themselves "the Chosen Few."

The animatronic puppet suit for Hoggle from the Jim Henson cult classic Labyrinth got lost in someone's luggage at an airport. By the time it was found, most of the foam had deteriorated, revealing the (slightly terrifying) metal skeleton underneath. Hoggle was painstakingly restored and now lives in a display case in the resale outlet for belongings lost at airports in Scottsdale, AZ.

The offspring of a male lion and female tiger is a liger. A female lion and male tiger producer a tigon. Tigers, lions, leopards, panthers, and female hybrids (because males are sterile) can all interbreed, with names becoming increasingly complex. If a jagupardess, the offspring of a female leopard and male jaguar, mate with a tiger, she produces a tijagupard.

September 3, 1967, was Dagen Högertrafikomläggningen, or the Right-Hand Traffic Diversion Day, in Sweden, when traffic was changed from driving on the left-hand side of the road to driving on the right. The change-over went surprisingly well and initially produced a reduction in accidents, but those returned to "normal" levels within six weeks.

The Apollo program astronauts had to poop into plastic bags, then mix the poop with antibacterial gel, so it wouldn't decompose and produce gas that would burst the bag. The bags had a habit of coming unsealed, anyway. Official NASA missions transcripts contain multiple discussions of poop floating through the ship.