Deep sleep is the third stage of sleep that is responsible for repairing and restoring the muscles and your brain. In order for you to wake up feeling refreshed, you must spend part of your night in deep sleep. Getting enough deep sleep will benefit your memory, muscle growth, and immune system. Without enough deep sleep, you may have learning difficulties, increased risk of infection, and long-term health conditions. Continue reading to learn more about derp sleep and about how much you need.