After water and air, sand is the natural resource that we consume more than any other--even more than oil. Every concrete building and paved road on Earth, every computer screen and silicon chip, is made from sand. From Egypt's pyramids to the Hubble telescope, from the world's tallest skyscraper to the sidewalk below it, from Chartres' stained-glass windows to your iPhone, sand shelters us, empowers us, engages us, and inspires us. It's the ingredient that makes possible our cities, our science, our lives--and our future.And, incredibly, we're running out of it.