Why do we need to sleep?

Wiki: "The multiple theories proposed to explain the function of sleep reflect the as-yet incomplete understanding of the subject. (When asked, after 50 years of research, what he knew about the reason people sleep William Dement, founder of Stanford...

I got to thinking about this, and was wondering why some people need more sleep than others. For example, all my housemates go to bed at a similar time (10-11pm) but we all wake up at different times. One of my housemates naturally wakes up at 6.30am...

i m 34 yr old man, single, work as an architect. i m 183cm (6ft) and about 115kg.. yes i m over wieght. and i dont workout at all, and as i m signle it is very rare to eat a home made food.. just fast foot restuarant and frozen things that can heated...

I'm not on drugs. I don't drink caffiene. I'm not an insomniac, because I *could* sleep every day if I wanted to, but I don't need to sleep because I'm not tired. I'm not on any medications. I don't have any mental disorders (well, none that im aware...

Lately, I just don't seem to get tired. I don't drink coffee or anything, so caffeine's not the issue. I just don't ever feel like or want to sleep. I mean, I can and I do, but it's not because I feel tired, I just go to bed because I feel like it would...

Why do we have to sleep? Why couldn't we have been designed to not sleep? I know that sleep helps the body to rebuild, to reorganize the thoughts, etc. etc. That's the PURPOSE of sleep. However, I want to know WHY? Why are we made this way? What are...

Is there a chemical basis "restfulness"? Is something (a substance) removed (or replaced) to refresh us during sleep? Have any studies been done (on, say, the composition of CSF) of rested and sleep deprived individuals?

I've noticed the more exercise I do, the less sleep I need. I work from 3pm-1130pm and when I wasn't seriously working out, go to bed at 2am and not wake up until 11am. Now if I go to sleep at 2am, I try to sleep till 10 but by 9am my body keeps waking...

I have an almost 3 year old little girl who Will not take naps and when it comes to night time she will not go to bed till 2-3am. ( even then she will hum and sing in her room) I don't know why this is happening. She is running on 4-5 hours of sleep...