Many people suffer from an occasional nightmare.
Others suffer the terrifying, seldom remembered horror of night terrors. There are five stages of sleep ranging from stage one, a very light sleep, deeper and deeper into stage four, a deep, restorative sleep. If you were to watch someone during this phase of sleep, you could see the movement of the eyes beneath the closed eyelids. Dreaming Dreams, nightmares, night terrors. They all disrupt sleep and often cause groggy days and a great deal of yawning.