A-listers from Miranda Kerr to Chrissy Teigan are all doing it. But what the heck is dry brushing, exactly? Believe it or not, this viral beauty trend is actually pretty old. In fact, we’re talking ancient. It comes from the Ayurvedic practice called garshana and it’s been practiced by people for thousands of years. Here’s what you need to know about this old-made-new beauty ritual.