Anyone who’s ever gotten a bad night’s sleep knows that the effects show up in the mirror the next morning: dark circles, breakouts, sallow skin… the list goes on. Along the same lines, jet-lagged skin can look pretty rough, too. (Otherwise, nobody would need those giant sunglasses post-flight, right?)The common thread between the two is your circadian rhythm—the 24-hour cycle that’s governed by your body’s biological clock, primarily responding to light and darkness. And while your circadian rhythm isn’t the first thing that comes to mind when you think about your skin, research shows it’s actually crucial for maintaining a healthy, resilient and (you guessed it) younger-looking complexion. “The skin is the body’s largest organ and it responds to circadian rhythms in a manner similar to other organs,” says Tina Alster, M.D., director of the Washington Institute of Dermatologic Laser Surgery and clinical professor of dermatology at Georgetown University Medical Center. “If it’s disrupted, your skin will visibly suffer.”MORE: How Poor Sleep Ages YouIt all has to do with your skin’s stem cells, explains New York City dermatologist Eric Schweiger, M.D. “Studies show that skin stem cell activity varies depending on the time of day,” he says. For instance, an October 2013 study published by Cell Press shows that during daylight hours, your skin’s stem cells switch on certain genes to defend themselves from UV light, which unleashes damaging (read: aging) free radicals on your skin. Daytime defenses also work against other environmental stressors, such as pollution, that contribute to aging by breaking down healthy skin cells, Dr. Schweiger explains.At night, on the other hand, while you’re snoozing away in the dark, your skin’s stem cells don’t need to go into defense mode. “Instead, they can focus on producing healthy cells to replace the damaged cells,” says Dr. Schweiger.According to research conducted by skincare company Amore Pacific, your skin’s natural antioxidant protection is highest between the hours of 7 and 11 a.m. (giving your skin a much-needed boost in fending off those daytime free radicals). On the flip side, skin reaches its peak reparative levels between the hours of 10 p.m. and midnight.MORE: 7 Habits of Women With Great SkinYou run into trouble when your skin’s circadian rhythm is disrupted. When that happens, your skin isn’t able to fend off damage or repair as effectively. “As a result, collagen and elastin in your skin may continue to break down,” says Dr. Schweiger. “And without that ‘repair’ cycle, wrinkles will form and skin laxity may increase.”And not only that, research from the Centre for Genomic Regulation found that when your skin’s circadian rhythm is impaired, you may be more susceptible to skin cancer as well. “It’s yet to be proven,” Dr. Schweiger notes, “but studies suggest that chronic lack of sleep can decrease the regenerative properties of the skin and may even lead to a great risk of tumor development.”So what can you do about all this? First, don’t freak if you’ve gotten a few bad nights of sleep. “If you experience inadequate sleep once in a while, your skin won’t be as stressed as it would be from chronic circadian rhythm disruptions,” says New York City dermatologist Francesca Fusco, M.D. Just try to get back on track as soon as you can.Second, stack the deck in favor of your skin with products that help your skin’s circadian rhythm function in a healthy way. This is especially important as you age, since a study from MIT found that circadian function actually decays as the years go by.At night, use a retinol or prescription retinoid to stimulate additional skin cell turnover. “This helps your skin cells produce healthy collagen and elastin, keeping your skin as smooth and wrinkle-free as possible,” says Dr. Schweiger.MORE: The Importance of CollagenNight is also the perfect time to treat skin to an intense does of hydration, since sebum production (aka your skin’s natural oil) is lowest while you’re sleeping. “Night is an optimal time to hydrate skin with powerful humectants like hyaluronic acid, which attract and bind moisture hundreds times more than its weight,” says Dr. Fusco.During the day, boost your skin’s levels of natural antioxidant protection with a broad-spectrum sunscreen that contains additional antioxidants. “Sunscreen is necessary even when you’re in the car or taking a quick walk down the block,” says Dr. Schweiger. “It helps protect your skin against both the development of skin cancer and skin cell breakdown from sun exposure, which leads to increased skin laxity, sun spots and the development of fine lines and wrinkles.”Check out a few products below and get your skin back in sync, but keep in mind that we’re dealing with brand new science here, and much like how the first computers were crazy-expensive, the luxury skincare brands are the first to jump on this research. If the sticker price is too much for you, it’s likely the technology will trickle down to drugstore brands in a year or two, so keep an eye out.