Water is our most familiar chemical companion. It’s the smallest and simplest of the basic food molecules, just three atoms: H2O, two hydrogens and an oxygen. And its significance is hard to overstate. Leaving aside the fact that it shapes the earth’s continents and climate, all life, including our own, exists in a water solution: a legacy of life’s origin billions of years ago in the oceans. Our bodies are 60% water by weight; raw meat is about 75% water, and fruits and vegetables up to 95%.