How Keys Work Inside Pin-Tumbler Locks (VIDEO)

They protect our homes, our cars, and our most valuable possessions--but did you ever wonder how keys work? Do you even know what the inside of a lock looks like?

Check out the strangely mesmerizing YouTube video above to see exactly what happens when you insert a key in a lock and then give it a turn. The animation shows a so-called pin-tumbler lock, in which small pins line up with grooves in a key before the key can turn.

The technology isn't exactly new. An article published in the November 1946 issue of Popular Science describes how it all works: "As the key turns, the pins divide along the edge of the cylinder, permitting it to revolve... When the key is withdrawn the pins will fall out of line again, freezing the cylinder into place."

The modern pin-tumbler lock and flat key, invented by Linus Yale Jr. and patented in 1861, was inspired by locks linked to ancient Egypt. Archaeologists have yet to pinpoint exactly where and when the very first lock was invented, but researchers suggest wooden tumbler locks were used as far back as 4,000 years.