Book excerpt: One man's passion for perfume leads him to explore one of the most intriguing scientific mysteries: What makes one molecule smell of garlic while another smells of rose? In this witty, engrossing, and wildly original volume, author Luca Turin explores the two competing theories of smell. Is scent determined by molecular shape or molecular vibrations? Turin describes in fascinating detail the science, the evidence, and the often contentious debate—from the beginnings of organic chemistry to the present day—and pays homage to the scientists who went before. With its uniquely accessible and captivating approach to science via art, The Secret of Scent will appeal to anyone who has ever wondered about the most mysterious of the five senses.