Yet despite its fundamental importance in our mental life and in the existence of all animals, our scientific understanding of how smell works is limited. In this Very Short Introduction, Matthew Cobb describes the latest scientific research on smell in humans and other mammals, in insects, and even in fish. He looks at how smell evolved, how animals use it to navigate and communicate, and disorders of smell in humans. Understanding smell, especially its neurobiology, has proved a big challenge, but olfactory science has revealed genetic factors that determine what we smell.