If you’ve ever hugged a tree (and we hope you have!) you’ll know that the outside of a tree can be bumpy, prickly, and can even scrape your skin. That’s because trees are covered in tree armor – otherwise known as bark. One of our listeners wanted to know what tree bark is made of, so we asked forest ecologist Diana Macias to explain. Do you have an evergreen question for Moment of Um? Leaf it for us at BrainsOn.org/contact, and we’ll try to find the answer.