Ever wonder what the inspiration was behind sheet masks? Or exactly why Koreans are obsessed with fermented ingredients in skin-care products? It's time to take a history lesson. (Trust us, this won't be boring.) Alicia Toon, the founder of Peach and Lily, one of the best Korean beauty sites in the world, recently took a trip to Korea to explore the country's history of beauty rituals. "While Korean beauty innovations and the latest K-beauty trends have been the buzz, I love the timeless Korean beauty ingredients and rituals that have been passed down through the generations," says Yoon. "A lot of this actually informs what we see in the marketplace today, since that beauty tradition is so deeply engrained in the Korean beauty consumer's mindset." Here, she breaks down five ancient Korean beauty rules that influences what we see in today's most popular products.