Why Do We Sleep?

Curious about this activity we all do without understanding why, I began a quest to research the process of sleeping in terms of biological, physiological and also mental and emotional standpoint. What is it that happens when we sleep? Where does our consciousness go? Why is sleep so important? Is there such a thing as too much or too little sleep? I might not be able to answer all of these questions but surely will begin unveiling some tremendous benefits of sleep.