This book was conceived as a tribute to one of the founders of the psychological study of the sense of smell, Professor Trygg Engen. The book is divided into four sections. The first reunites the fields of psychophysics and the perception of environmental odours and discusses the impact of odours on beliefs and expectations. The second addresses cognitive processes in olfaction, how odours are interpreted, lexicalized, associated with contexts and remembered. The third focuses on the cerebral bases of olfactory awareness and the neuropsychological investigation of olfaction with special emphasis on olfactory dysfunctions, and the last concerns affective and developmental processes in olfaction. The aim in producing this book is that it will help promote further research in olfactory cognition and attract new inquisitive scientists to the field.