Eyebrows are the Swiss Army Knife of the human body—they do everything! First and foremost, they protect your eyes. The shape of the brow ridge and the brows themselves channel sweat, rain, and moisture away from the eyeballs so your vision stays clear. Second, they’re essential for nonverbal communication. Scientists who study facial expressions say eyebrows are key to expressing happiness, surprise, and anger. They’re especially useful to speakers of sign language, who contort their eyebrows to complement hand signs. Additionally, they act as an ID card. Eyebrows stand out against the forehead, can be clearly seen from a distance, and don’t change very much over time—making them perfect for identifying people. In a 2003 study at MIT, people were shown a picture of Richard Nixon with his eyes Photoshopped out and then a picture with his eyebrows erased. They had significantly more trouble identifying Tricky Dick and other celebrities when the brow was bald. The takeaway? If you’re going undercover, forget the sunglasses. Shave your eyebrows instead.