Every wonder why you tend wake up with a hard-on? It certainly makes it hard to pee when you first wake up (no pun intended). Well, thanks to our friends at ASAP Science, you can get this particular sex-ed lesson that you never had in school.

In the following video, ASAP Science looks at the hard facts and some of the biology of an erection to discover the mechanism behind the phenomenon. As explained in the video, morning wood effects grown men, little boys, and even happens to males still in utero. Two terms you’ll learn in the video included norepinephrine and vasoconstriction. Find out what they mean and also how the bladder sometimes has a role in all of this as well.

Other interesting ASAP Science topics we’ve covered on Homorazzi include: “The Science of Orgasms“, “The Scientific Cure for a Hangover“, and “Could A Zombie Apocalypse Ever Exist?” Learn about morning wood below!

The Science of ‘Morning Wood’

The lesson was written and created by Mitchell Moffit (twitter @mitchellmoffit) and Gregory Brown (twitter @whalewatchmeplz).