From Dream land
Dreaming might help the brain eliminate any unnecessary information or memories while processing and storing what’s important. Some people feel more refreshed after having had slept and dreamed, even if they do not remember dreaming.
People are most likely to remember the last dream they’ve had in their sleep cycle. But it’s possible to remember a vivid dream long after it’s occurred if it seemed very intense.
Vivid dreams can be positive or negative, realistic or fantasy. Scientists know that most heavy dreaming occurs during rapid eye movement (REM) sleep. REM sleep normally cycles every 90 minutes during a night of sleep and may last 20 to 25 minutes.