Not everybody has the same sleep cycle, but there is a kind of average cycle that has a fairly regular pattern. Sleep actually has four stages. When you go to sleep you pass through stage 1 where you experience a dreamlet. Its technical name is 'hypnagogic vision'. It lasts only a very short time. From there you drop straight into stage 4 which is deep sleep without dreams. In that stage your brainwaves are calm and slow. You stay in that stage for 90 minutes. When the 90 minutes are up you rise to stage 1 again which is close to waking. Because of this your brainwaves are short and quick like in the waking state. You then dream for about 5 minutes.
Sleep scientists can see that the sleeper is dreaming by two signs: one is REM or Rapid Eye Movement. The eyes of the dreamer move rapidly from side to side. The other sign is marked on continuous paper of the EEG or the ElectroEncephaloGraph. This is a machine that records your brainwaves which give off low electrical currents.
After this first phase of full-on dreaming you sink again into stage 4 of dreamless sleep. Not quite as deeply as the first time. You stay there for another 90 minutes. And then you come up again to stage 1 with the fast brainwaves and you dream for about 10 minutes, after which you go down into deep sleep, which however is not as deep as before. Yet it is still a NREM stage which means no eyes flickering and no dreams happening.
Depending on your sleep cycle you will have three to four REM episodes with dreams. The last dream is usually about 20 minutes but may last up to 40 minutes. The dreams you normally remember are from this last dream phase. Mostly the last few minutes before waking up are usually remembered.
It is interesting to note that these REM or dream bouts are like different acts in a stage play. When you go to sleep you are actually going to a NIGHT SHOW. Pity to forget most of it for it is fascinating to see how each scene of those three or four acts is intelligently integrated like in good film or stage play.
Another interesting thing is that your last thoughts before you drop off to NREM deep sleep are taken up by that first dreamlet. And then, when you come up from stage 4 to do your first act of dreaming, the thoughts or theme of that first dreamlet is spun out into a little yarn. And this happens all through the night during the REM activity.
And no less interesting is the fact that the very last thing you dreamt about is going to appear first thing when you wake up in the morning. So you can see that dreaming and waking are intelligently connected.
Another interesting fact is that babies in the womb dream more than new born babies. They are being prepared for their life out of the womb. Once they are out of the womb, the new born have a different dream pattern. They dream every 50 minutes instead of every 90 minutes.
What is particularly interesting with babies is that their limbs are not as paralysed during sleep and dreaming as those of the dreaming adult. It looks as if their dreams were teaching and training their limbs, thus preparing them for their waking life.
Kurt Forrer Dream Interpereter