Guys of every age know all about it – girls too, by association. It’s morning wood, and it’s a problem/gift for all males from the uterus to the grave. Of course, we know the what and when of it. But do you know the why and how?

Our favorite YouTube illustrators AsapSCIENCE have just posted their latest simplified science episode, and it tackles the physiology behind the REM tent. Check it out:

Previous episodes of AsapSCIENCE have tackled the real possibility of a zombie apocalypse as well as the famous Monty Hall problem. Go ahead, hit yourself with some knowledge.