“Sand is the main material that modern cities are made from. It is to cities what flour is to bread, what cells are to our bodies”, says the journalist Vincent Beiser in his book “The World in a Grain: The Story of Sand and How It Transformed Civilization.” Even though the sand is hidden from our eyes, it is everywhere around us. We use it not only for making glass, steel, and concrete -the fundament of every modern city -but also for paint, computer chips, and even toothpaste. We use sand so much that, besides water, it is the most relevant resource in the world.