Historically, scientists saw no need to understand the science of sleep because they thought it was nothing more than a state of inactivity. What would be the point in studying humans doing absolutely nothing? It was only until much later as technology developed that scientists were able to see that sleep, despite appearances, isn’t a state of inactivity at all, and that in fact the brain and body are actually very active during sleep.

Like many academic subjects sleep can appear to be a big and confusing subject, but it needn’t be. Here’s a quick overview of the science of sleep, explaining exactly what happens when you fall asleep and the different stages of sleep you enter into during the night as part of your sleep cycle.