Someone has said, "Blessed is the person who is too busy to worry in the daytime and too sleepy to worry at night." True that is! Indeed, sleep is bliss. Sleep deprivation increases the risk of heart disease and diabetes. Lack of sleep impairs grasping and learning, and reduces attention span. It burdens the brain and affects its functioning negatively. A sound sleep helps one get rid of physical tiredness and relieves mental fatigue. Benefits of sleep include improved memory, increased creativity and a longer and healthier life. Adequate sleep is an important part of a healthy lifestyle. Sleep is a natural phenomenon of the state of rest. Regular sleep is essential for survival. Interestingly, its true purpose is still being researched. Researchers have not yet obtained conclusive results about the exact purpose of sleep. Moreover, it is interesting to observe that our sleep undergoes a series of stages. The states alternate between deep and light sleep. According to the basic classification of the various stages of sleep, it is grouped into two distinct stages, namely, REM and NREM. REM sleep is characterized by a rapid movement of the eyes, as also a very low muscle tone that is typically seen in mammals. Most of the dreams that you remember after awakening from sleep, are those occurring in the REM stage. This stage is characterized by brain activity and increased rate of respiration. REM sleep is also known as paradoxical sleep as it is an unusual combination of increased brain activity and muscle immobility. The NREM, which is known as the non-REM sleep has four different stages. A comparatively lesser amount of dreaming occurs during this stage of sleep. Movements of limbs or even sleepwalking are observed during the non-REM stage. The four stages of the NREM sleep are simply named as N1, N2, N3, and N4. Stage N1: This is the phase of drowsy sleep, during which you may experience hallucinations and sudden twitches. It is during this stage that you may lose your muscle tone and your conscious awareness. This stage of sleep is characterized by brain transitions from alpha waves to theta waves and is primarily the stage when sleep starts laying her hands on you! Muscle activity is reduced, eyes are closed, but awakening from this stage is relatively easy. It is common to experience a feeling of falling, during this stage. Stage N2: During this stage of sleep, muscular activity further reduces and awareness of the external environment vanishes. Sleep spindles, the bursts of brain activity during which the brain tries to stop processing, characterize the N2 stage. In short, this stage is when the brain succumbs to sleep. During this stage, there is an alternation between muscle activity and complete muscle relaxation. The heart rate lowers and body temperature reduces. Stage N3: Walking in sleep or sudden feelings of terror when asleep commonly occur during this stage. Bed-wetting may also occur. N3 is mostly only the transition to the fourth stage. It is a phase of deep sleep. Stage N4: It is a stage of even deeper sleep. According to some researchers, the third and fourth stages of sleep can be combined and together called delta sleep. This is when you are fast asleep. Tissue growth and repair occurs during stages 3 and 4. It is during these stages that you energy is restored. A majority of the night's sleep is non-REM while a small part of it is REM. We need 8 hours of sleep daily, which means, one-third of the day should be spent sleeping. Considering it to be a period when we are doing nothing, sleep is neglected and quite sadly so. Sleep is in fact that period of the day, when the body gets its much-needed rest and the brain gets time to recover from energy losses, enable tissue repair, and restore its performance. A sound sleep is when you are switched off from the worries of daily life. It helps maintain overall health and is essential for your physical and mental well-being.