How sleep works: The reasons why we can't live without it

If you are one of the millions of people who always feels tired, you can blame it on your alarm clock, the industrial revolution and a general lack of understanding about the bodily behaviour. Or, maybe it is because you sleep too long.

It turns out the human body has an internal clock that is so precise, there are many factors that can cause you to wake up tired.

One thing that is known for sure - if you are not hitting every sleep cycle, you are not getting a good night's rest.