We can say that we recharge our energy during sleep. However, scientific studies have not proven this yet.  Despite this, if we do not sleep even 1 night, all our activities slow down on the next day due to adrenaline.  People who do not sleep for 2 days in a row are in a worse situation. Attention and concentration decrease and errors increase. After 3 days, people start hallucinating and clarity of thought is lost. Subsequently, people are disconnected tom the real world. It is proven with experiments on mice that keeping a living being awake can cause death.

One of the 2 occurrences during sleep is the excretion of growth hormones in children while the other is excretion of chemicals necessary for our immune system.

There are numerous theories on why we sleep.

• Sleeping gives the opportunity to repair the muscles and other tissues and renew the cells that are dead or close to death. 
• Sleeping gives the chance of arranging and archiving the information in the brain, and forgetting unnecessary ones.
• Sleep increases our energy saving. Thus, we are able to live with 3 meals a day instead of 4-5 meals.
• Sleep may be the recharging period of the brain that is continuously functioning all day. It can increase the energy necessary for the brain cell activities by reducing the energy consumption in other organs. All we know  about sleep is that if we sleep well at night, we feel good in the morning and both our body and mind are refreshed.