Even when you're fast asleep, your brain continues working. Processes information, regulates important functions and helps organise memories from the day.

As you get ready to go to sleep, your core temperature drops naturally. This is a normal part of your body's sleep pattern and plays a role in maintaining a healthy sleep pattern.

Suddenly, just as you're going to sleep, it is possible to experience a jolt as though falling to sleep. These movements are known as hypnic jerks, and they are seldom harmful.

In REM sleep, your eyes dart under the eyelids. It is during this stage that one experiences vivid dreams and brain activity.

Sleep is an important constituent to the consolidation of memory. While you sleep, your brain is enhancing and consolidating some memories, thus assisting learning and recall.

Most voluntary muscles are temporarily paralyzed in REM sleep. This is a natural phenomenon that helps to prevent you from physically acting out most of your dreams.

Growth hormone is secreted by the body during sleep, especially during deep sleep. It aids in the growth, repair of tissues and in some important body processes.

During many stages of sleep, your heart rate and blood pressure generally decrease. Your cardiovascular system receives a break in activity, compared to much of your waking day.

Your immune system is working during sleep and creating substances that regulate immune responses. Good sleep can keep immune function normal.

People and places might be familiar and situations can be very unrealistic. Although dreaming occurs in different sleep stages, vivid dreams are particularly associated with REM sleep.