Ed Conway is the economics editor at Sky News in the UK. For his new book, Material World: A Substantial Story of Our Past and Future, he traveled the globe to tell the story of six materials — sand, salt, copper, iron, oil and lithium — and how they have become so vital to modern economies. Along the way he illustrates the supply chains involved in producing and using these substances, and discusses the trade-offs involved that touch on geopolitics, the energy transition and much more. In t