Dreaming

Scientists describe dreaming as a way to organize our thoughts.Well this has been a really research topic for scientist for a extent period of time. They exist five stages of sleep. 1) The first stage is the beginning of the sleep cycle it is to considered as the transition period between weakfulness and sleep. this stage lasts approximately 5-10 minutes. 2) In stage two the brain begins to produce bursts of rapid
 rythmic brain activity. Our body temperature starts to decrease and heart rate slows. This stage it is for approximately 20 minutes. 3) In this stage is known as the transitional period between light and very deep sleep. 4) In this stage it is reffered as delta sleep because of its slow brain waves. Stage 4 is a deep sleep that lasts or 30 minutes approximately. Finally stage 5 most dreaming occurs in stage 5 it is know as the rapid eye movement REM, it increases respiration rate and brain activity. REM sleep is also known as paradoxical sleep because when braind systems become more active muscles get relaxed. Dreaming mostly occurs due because of increased brain activity. To enter to these stage its a long process because after stage 4, stage 3 and stage 2 are repeated before entering REM sleep.   

http://www.free-extras.com/images/sleeping_and_dreaming-1727.htm