I wondering what actually happens when you brew coffee (or tea) with hot water. Every source I can find simply talks about how long you need to brew it to "draw out" the flavor or "release" the caffeine. I'm interested in what's actually physically happening to the coffee grounds that makes it change the water into coffee. If it was just that particulate matter got into the water, there wouldn't be need for hot water. Is it that some small component of the coffee ground is actually changed from a solid to a liquid from the hot water and gets mixed with the water? Or maybe there's some microscopic pockets in the coffee ground which when heated expands and pops open releasing stuff into the water? What's actually going on? Thanks!