A famous British poet once wrote:" Oh Sleep!It is a gentle thing,Beloved from pole to ploe."As the scientists have studied sleep and dreams for years,they get a conclusion about sleep:There are two kinds of sleep--REM and NREM.NREM is divided into three stages.In stage one,you may be woken up by the noise .In stage two,a noise will probably not wake you.In stage three,the brain waves are less active.Then ,within another half hour ,you reach NEM sleep.This stage might last for an hour and a half and is the time when you dream.For the rest of the night,REM and NREM alternate.
Does dream do good or bad to you?The researchers say that normal people may have four or five REM periods of dreaming a night. Within the normal times,dreams have positive effects on our lives.It can make your brain take a good rest and make you learn new things better.So keep to sleep well and have a sweet dreams!Because we spend a third of our lives sleeping.