One of the fascinating things about sleep is we tend to think, oh, nothing's happening. I'm not getting anything done. But your brain is hugely at work. There are all these different stages of sleep where you can see these symphony of waves, where different parts of the brain are talking to each other, essentially. And so, we know for a fact that some of these stages of sleep, what happens is the brain will flush out toxins, like the amyloid protein that can build up over the course of a day. So just by virtue of that function, sleep is very important. But then on top of it, what we can see is that the neurons that were active during a particular experience, have come back alive during sleep. And so there seems to be some processing of memories that happen during sleep, and that the processing of memories can sometimes lead to some parts of the memory being strengthened, or sometimes you're better able to integrate what happened recently with things that happened in the past. And so, sleep scientist Matt Walker likes to say that sleep converts memory into wisdom, for instance.