People need at least 8 hours sleep at night. People need to sleep because it is the time where your brain can sort things out and time for you to relax and get energy for the next day.
Missing one nights sleep will make you cranky, missing 2 nights sleep will make you forget things and not be able to concentrate and not do normal tasks you would be able to do if you do sleep. After a while of not having any sleep the brain shuts down and will not be able to function properly this is really bad, and not good for anyone.
