Salt is found on most dining tables and in most kitchens—but this ubiquitous household item has a long and curious history. It’s a flavor enhancer, an ice melter, has been used as a currency, and has shaped civilization. Mark Kurlansky, author of  Salt: A World History, and Dr. Sonia Angell, Director, Cardiovascular Disease Prevention and Control, New York City Health Department, explain what salt is, where it comes from, and discusses its influence on history and on our health.