And by the 11th century, the Chinese were writing down their recipe for a mixture of salt, peter, sulfur, and charcoal that we now know as gunpowder. That becomes kind of a big deal in history, paving the way, as it does for modern warfare and arena rock pyrotechnics and... Oh, that's why! Not so dark after all. Thanks for watching. We'll see you next week. Crash Course is produced and directed by Stan Muller. Our script supervisor is Danica Johnson.