I am just wondering why people dream during naps? They are usually shorter than normal sleep and are in no way part of a sleep schedule. I understand that sleep cycles take at least 90 mintues to begin and finish and REM sleep becomes longer after hours of sleep. So why do we dream during naps?

P.S. everytime I have had a nap I have come at lot closer to becoming Lucid, i also have very vivd dreams during naps, more so than regular sleep. Any Reason?

Thanks