The clitoris. For thousands of years, humans (some of them, anyway) have known that you can give pleasure to its owner if you play with it in the right way. But it wasn’t until 2009 that science understood how it actually worked. Discover… the Mystery of the Clit!
https://gizmodo.com/until-2009-the-human-clitoris-was-an-absolute-mystery-5876335
