Bedtime. Depending upon what your age, you view it differently. If you’re a toddler or young child, it’s something you fight against because you’d rather stay engaged with the interesting things going on around you. If you’re a teen or young adult, you probably do the same! As an adult you view it for what it’s meant to be – a time for your body to regroup and rejuvenate, to take a break from the day’s activities and stress. When your body’s sleep cycle is working the way that it’s supposed to, it feels as though everything simply shuts down … and that’s what scientists thought for many years. But as researchers have spent more time and developed more exacting tests, they’ve learned that sleep is as complex a process as any that the body undergoes, and is just as necessary. So what exactly happens after we’ve brushed our teeth and tucked in? Well, to simplify things as much as possible, we rotate back and forth between two distinct types of sleep: non-REM sleep, or quiet sleep, and REM sleep, or dreaming sleep. Non-REM sleep is the sleep that we feel ourselves sinking into – at least when we first close our eyes. It is what happens when the body first starts to relax after closing the eyes and shutting out all of the stimulus that comes with what we see. Our breathing and thought patterns slow, our body and brain temperatures cool, and we relax. This sleep stage is divided into four separate categories of different depths, but in all of them the body is ready to move if it needs to. The deepest stages of non-REM sleep are when our bodies heal the most and prepare themselves for whatever the next day will hold. [caption id="attachment_77" align="alignright" width="300"] Good Sleep Starts at the Surface![/caption] REM sleep is when we dream. Our brains are incredibly active – in some ways it is twice as active as when you are awake – but our bodies are paralyzed. Just as quiet sleep heals the body, REM sleep seems to restore the mind, clearing out the extraneous information and allowing us to learn more easily and remember things more readily. People who have a healthy sleep cycle go back and forth between non-REM sleep and REM sleep several times a night in a predictable pattern. Though there are expected differences between the sleep pattern experienced by young and old, all healthy sleep cycles include and need a rotation between the two types of sleep. Though we may feel that we are in control of our bodies and how much sleep is enough, there is a natural drive for sleep that is controlled by both the amount of time since we last slept and by whether we have accumulated a sleep deficit. The ability to have this healthy cycle are influenced by a variety of things, including exposure to light and time cues that we expose ourselves to. These include clocks, calendars, and our social or work calendars, all of which have an impact on how well we sleep.