When we turn on the faucet or twist open a tall plastic bottle, we usually don't give a second thought to where our drinking water comes from—but how it gets from the ground to the glass is in fact a complex topic at the heart of civilization itself. Is it safe to drink tap water? Should you feel guilty buying bottled water? Is your water vulnerable to terrorist attacks? And with springs running dry and reservoirs emptying, where is your water going to come from in the future? Law professor and environmental policy expert James Salzman explains how drinking water highlights pressing issues from globalization and social justice to terrorism and climate change.