Sand is so tiny and ubiquitous that it's easy to take for granted. But in his book The World in a Grain, author Vince Beiser traces the history of sand, exploring how it fundamentally shaped the world as we know it. "Sand is actually the most important solid substance on Earth," he argues. "It's the literal foundation of modern civilization."

Plus, Roman talks with Kate Simonen of the Carbon Leadership Forum at the University of Washington about measuring the embodied carbon in building materials.

Built on Sand