The alien and Guardian of the Galaxy known as “Groot” is a tree. He looks like a tree, grows like a tree, and even sounds like a tree…I guess. In fact, Groot looks and acts so much like a tree from Earth that he is made from something you probably wouldn’t expect.

In my latest Because Science, baby Groot and I are trying to figure out what he’s really made of. You’re probably thinking, “wood, duh,” but even with Earth trees this isn’t the case. What makes up the majority of a tree’s mass is a question that scientists have been pondering for literally hundreds of years. It was only in the last few decades that we learned pretty much everyone on the planet has a misconception about where trees come from.

I don’t want to give away any spoilers before you watch my latest episode above, but I will say that once you understand where Groot gets most of his mass from–what he regrows from baby to big Groot with–you’ll know why the bond between the Guardians of the Galaxy is even stronger than that scene where Rocket is crying and you totally didn’t cry either.

Check out my last video on how lightsaber colors prove the weapons aren’t “laser swords,” subscribe to this playlist to stay current with the show, buy a Because Science shirt, mug, or collectible pin (you know why), and follow me on Twitter or Instagram to give me a suggestion for the next episode!