Abstract: Sleep is a naturally life style of the zoological species like human, animals, birds, mammals, Reptiles etc. The some species sleep time eye is open & mostly eye is closed. Different-different species sleeping time is dissimilar. The human sleep timing is dissimilar to born to older adults. Sleep is not functioning properly i.e. many disease is generated i.e. Blood pressure & other sleep disorder. Sleep is measured in different-different signal i.e. EEG, EOG, EMG signal. The stages of sleep are measuring a wave, O wave, delta wave. Stages of sleep are basically in two part Non REM and REM stages.
Keywords: Sleep, Stages of Sleep, Non-REM stage, REM stage.