Dreams are defined as images, emotions, ideas and sensations that involuntarily occur during REM sleep. Throughout the centuries, they have been extensively studied in the field of oneirology. But up to now, no MENSA genius has been able to determine the purpose of dreams. While research about dreams remain nascent, we still have discovered quite a few interesting facts about dreams thus far. Read on to familiarize yourself with the 21 most interesting dream factoids that have been unearthed so far: