Finnish sauna, Roman balneae, Japanese onsen, and Indigenous American sweat lodges are just a few examples of how cultures across the globe have long considered exposure to extreme temperatures therapeutic. But today scientists are only just beginning to unravel how and why this may be the case. So, what exactly is happening in your body when you feel the heat? Max G. Levy investigates. Lesson by Max G. Levy, directed by Noam Sussman, Ali Kellner, Homework Studio.