It’s a known fact that naps can boost alertness, mood, creativity, and productivity. In fact, naps have been around since humans first came into existence. They’ve touched all personalities, professions, and eras. Early Neanderthals took them after hunting woolly mammoths. After all, it was excruciating work. Thomas Edison was big napper and notably said he got most of his energy from them. John D. Rockefeller napped every afternoon in his office. And former president John F. Kennedy took frequent naps to break up his day. OK, so we know that most everyone naps, and that famous people, world leaders, and innovators nap, too.\nBut why do humans like to nap? What is it about a good snooze that’s so refreshing? Most mammals sleep in short increments throughout the day. Yet, humans have taken this to a new level and sleep in one long period. But our bodies are genetically programmed to have two periods of sleep. You guessed right that the first period is at night. And the second period is most often between 1 and 3 p.m. So, if you’re always wondering why you suddenly feel sleepy around that time, it’s not because of the enormous buffet lunch you just had, it’s actually built into your physiology. And what’s the cure for this feeling? A nap, of course!\nWhat Type of Nap Is Right for You?\nBecause sleep falls into cycles, the amount of time you sleep can make or break your nap. The longer you sleep the more sleep cycles you fall into to. If you catch the right pattern, you can wake up feeling refreshed and ready to go. If your alarm wakes you in the wrong cycle, you might be wishing you went to the coffee shop instead.\n\n15-25 minutes (a.k.a. catnap): Because you don’t fall into a deep sleep in this amount of time, it’s easier to hit the ground running after waking up. This short bout of sleep has been proven to help with alertness and concentration, mood elevation, and sharpening motor skills. A recent study on commercial pilots found that a 25 minute in-flight nap (while the plane is manned by a copilot of course) enhanced performance by 34 percent and overall alertness by 54 percent.\n60 minutes: This type of nap is known for improvement in remembering things, like names, faces, useless or important facts, what groceries to buy, that sort of thing. When you sleep for around 60 minutes, you fall into slow wave sleep, the deepest type of sleep. However, you may wake up feeling a bit groggy. See the “what to avoid section” below for an explanation.\n90-120 minutes: Looking to feel completely refreshed and wide awake? Try hitting the couch for around two hours, which comprises all stages of sleep, including REM and deep slow-wave sleep. These naps can help clear your mind and aid in creativity and emotional and procedural memory. A nap of this length is usually easy to wake up from.\n\nWhat to Avoid?\nUnless you’re going with a longer nap, try limiting your sleep to no longer than 30-45 minutes. Once you cross the 30 minute mark, you end up in a deep sleep cycle, which is difficult to wake up from. If you happen to take a nap of this length, you’ll most likely experience sleep inertia, or grogginess and disorientation that can last for half an hour or more.