When we say the brain, we specifically refer to like neurons or tissue within the cranium. Let's say brain tissue broadly. Well I imagine being a fat crosses the blood brain barrier, right? So it's not- Ah, wait, yes, but it needs to be in the blood first to cross theBlood brain barrier. And when it's in the blood, does fat just freely float through the bloodstream? Oh, it's probably bound to a protein. That's right. It's bound to protein and that protein can't cross the blood brain Barrier. So it just can't access it. But here's the first reason. If you were to take a molecule of glucose and