In addition to reducing how many highlights you get, Anderson says adding a root — a faux one! — is key to extending the lifespan of your highlights. A shadow root removes the the harsh line between your natural hair and where the highlights begin, so as the hair grows out, the transition from the new growth to the highlights is smooth. And if Margot Robbie co-signs a lived-in root , then so do we. “Margot’s root always looks modern and beautiful, even as it grows in,” Anderson explains. “The root looks so good, I almost have to convince her it’s time to come back and get highlights again. If I made her too blonde, without the root, she would be in my chair every six weeks. It would be so damaging.”