Alexandra Horowitz, author of the bestseller Inside of a Dog, explores what dogs know in even greater depth, following their lead to learn about the dog's spectacular nose and how we mere humans can improve our underused sense of smell. Here Horowitz, a leading researcher in dog cognition, continues to unpack the mystery of a dog's nose-view, in order to more fully understand our companions. She follows the dog's nose--exploring not only its abilities but the incredible ways it is being put to use. Because human noses are so inconsiderable in comparison--we have but six million olfactory receptor cells while dogs have hundreds of millions--we have difficulty conceptualizing what dogs can perceive. To a dog, there is no such thing as "fresh air." Every breath is full of information. Dogs, when trained, can identify drugs of every type, underwater cadavers, cancer, illicit cell phones in prison, bedbugs, smuggled shark's fins, dry rot, land mines, termites, invasive knapweed, underground truffles, and dairy cows in estrus. But they also know about the upcoming weather, earthquakes before they happen, how "afternoon" smells, what you had for breakfast, and whether a cat touched your leg yesterday. And of course, they know the distinctive odor of each spot of sidewalk as they travel home. In fact, what every dog knows about the world comes mostly through his nose. But the mysteries of the nose are not restricted to the dog alone. For Horowitz also delves into the abilities of expert human sniffers--from perfumers to sommeliers to animal trackers who use smell to search out their quarry. She also trains her own nose, smelling the streets of New York City and using the experts' methods to hone the human ability we all have but rarely use to its full extent. By observing everything from her own dogs to working detection dogs and human sniffers, Horowitz takes us along on her quest to make sense of scents, combining a personal journey of smelling with a tour through the cutting-edge science behind the olfactory powers of the dog. Writing with scientific rigor and her trademark wit, Horowitz changes our perspective on dogs forever. Readers will feel that they have smelled into a fourth dimension, literally broken free of human constraints and understood smell as never before; that they have, however fleetingly, been a dog.--Adapted from dust jacket.