Dr Rachel Sumner is a psychobiologist and chartered psychologist with the British Psychological Society Division of Health Psychology. She is a senior research fellow in the Health and Human Performance Global Academy at Cardiff Metropolitan University. Rachel researches areas that consider how our lived environment impacts our health and wellbeing, using a variety of methods and outcomes to try and make sense of the very complicated ways that make our health a function of our lived experience. She is an interdisciplinary researcher who has made her career in collecting knowledge from various fields and trying to bring it together to make sense of the ways in which our health can be made better or worse through our lived experiences. She was previously the course director for the MSc Health Psychology at the University of Gloucestershire, from which this book has been adapted. This book was developed from a module that was written to give health psychology trainees a comprehensive understanding of health from its very smallest indices (our cells) right up to its largest measure (our societies). Taking both critical social and community aspects of health provides a comprehensive and inclusive means of accounting for the incredible intricacies of health at the individual and population level. It is hoped that this book will provide a broad and integrated starting point for those interested in health psychology, whether they are psychologists, public health practitioners, in medicine, or in medical areas of the social sciences.