What we know about sleep and its importance has changed quickly over the past 20 years. This article at BioSource Software company is not a scientific study, but it provides an excellent overview of our current understanding of what happens during sleep, what happens as we age, and what happens when we deprive ourselves of sleep or do not sleep well. The beginning of the article is more neuroscience-oriented, so if you find it confusing, scroll down and you’ll find more straightforward information. It also contains a link to an interesting TED talk.