John Green teaches you about water! So, we talk about resources a lot on Crash Course, and today is no exception. It turns out people can't live without water, which means it's absolutely necessary for civilization. Today John talks about water in the context of classical civilizations, but not like Greece or Rome or something. We're talking about the Maya civilization in Central America, and the Khmer civilization in what is now Cambodia. So this is an awesome video, OK?