What doesn't science know? Can you list a few things (the more basic and surprising the better)?

Apparently they only discovered "aquaporins"- facilitated transport enzymes on cells that allow H2O in- in 2003. Very surprising, as H2O is not permeable to cellular membranes at a level that could explain the high diffusion levels in our cells, and science didn't understand before then how our cells were able to take in enough water. Things like this. Sleep, for instance. As I understand it, science DOES NOT fully understand the basics of why we even need to sleep (as distinct from mere rest).