Naturalist Diane Ackerman hosts this "Mystery of the Senses" installment of "Nova," which explores the sense of taste. Ackerman goes beyond the simple act of eating to examine the biology of taste and the important role of food in rituals and as delicacies. Ackerman gets secrets from a French chef, visits a family in Mexico as they prepare their Day of the Dead treats and heads to a Japanese restaurant that serves potentially poisonous fish.