As well as being a professor of neuroscience and psychology at U.C. Berkley, Mathew Walker is the founder and director of the Center for Human Sleep Science.  He shares his expertise on all things sleep related in his bestselling book Why We Sleep and his Ted Talk "Sleep is your Superpower."                                               Your Clever Brain -  As you sleep, your brain is solving problems and seeking unexpected patterns.  "By doing so, it can come up with these completely novel answers to previously unknown questions," Walker explains.                    Non-REM sleep helps strengthen and consolidate information you've accumulated throughout the day.  The brain compares new data with previously known information.  New connections are made, resulting in " system update" of sorts.                        New memories are cemented during non-REM sleep.  Walker describes this as the brain's way of "hitting the save button."  Memories are moved from short-term storage areas of the brain to the cerebral cortex, where long- term memories are filed.  The brain also seems to be deleting information that might be unnecessarily taking up storage space.                                            During REM sleep, your brain paralyzes your body.  This keeps you from hurting yourself by acting out your dreams.   REM sleep helps take the sting out of emotional wounds so that you feel better about hurtful experiences the next day.                         Notable Facts- Being a morning person or a night owl isn't a matter of personal choice.  An individual's chronotype-his or her natural inclination toward a particular circadian rhythm-is dictated by genetic imprint.                                          While you sleep, immune cells find and eliminate virally affected cells or tumor cells in your body.                          Sleep-deprived people can't accurately discern emotions through facial expressions.