It may seem as if dreams are just a chance by-product of sleeping but they may be the most important part of sleep for us. If we are deprived of sleep for any reason then the majority of our subsequent sleeping activity is dream-rich REM state sleep. After we have made up our sleep deprivation then our sleep and dream cycles quickly return to normal.
We tend to sleep in cycles of around 90 minutes and create a dream experience in each of these sleep cycles. In an average sleep of 7 to 8 hours, you will experience five of these sleep cycles and create five dream episodes within them. The first of these episodes last for around 10 to 15 minutes and the length of your dream episodes increases with each sleep cycle, reaching up to 40 minutes long with the final dreaming episode before waking.
Dreaming sleep is quite a light sleep and as you cross the threshold between dreaming and waking you experience what is known as the hypnopompic stage. At this point you will becoming more aware of your waking environment but will still be creating dream imagery. This can be an excellent opportunity to practice lucid dreaming.
The first stage in your sleep and dreaming cycle is known as the hypnagogic stage. This occurs as you begin to become more relaxed and drift off into sleep. It often takes the form of seemingly random flashes of imagery, most of it reflecting your days events. As your body naturally begins to relax, the residual tension that you have built up in your body during the day starts to fade away. At this point you may experience an involuntary twitch as the last of your bodily tension releases. This twitch is known as the hypnic jerk and can give the sensation of falling off an edge as you fall asleep.