Oh, so you think "Grumpy Cat" is cool? Bitch, please! This cat here has been grumpy (and still is) since Not to mention that he's a childhood favourite of everyone (including me)! Thank you, Jim Davis!
The US team believe the "waste removal system" is one of the fundamental reasons for sleep. Their study, in the journal Science, showed brain cells shrink during sleep to open up the gaps between neurons and allow fluid to wash the brain clean.