Nightfall refers to a health condition where there is an uncontrolled or involuntary ejaculation of sperm during sleep. The reason why this happens is sexual arousal and orgasm achieved during dreams. Also called as nocturnal emissions, this condition is quite common and normal for most males during the teenage and early adolescent years. In fact, this is one of the most normal kind of biological developmental activity.Some people believe that night discharges result from the stimulation caused by dreams and also the memories of the waking sexual activities of the individual. However, there are no evidential studies to support this theory.Some people even claim that they have bad discharge without even sexual dreams. Another theory states that wet dreams are the way in which the body throws away excess of semen, though this is not proved scientifically.