A critical mass of research linking early life events, experiences, and exposures with adult health conditions is delineating the developmental origins of many common chronic diseases. This emerging body of life course health development (LCHD) research specifies the complex adaptive processes by which both adversity and opportunity are integrated into developing biobehavioral systems. It is also challenging long-held views about origins and etiology of health and disease. There is a growing momentum among practitioners and policymakers to “connect the dots” between this rapidly expanding evidence base and the related practices and policies that are implemented within the fields of medicine, public health, nursing, mental health, education, urban planning, community development, social welfare, and others. At the same time, there is a strong impetus among LCHD researchers to continue to fill the substantial gaps in our knowledge and to ensure that research findings are appropriately synthesized and translated before being applied in clinical, public health, or public policy contexts. Comprised of 26 chapters that grew out of the 2013 Maternal and Child Health (MCH) Life Course Research Agenda-Setting Meeting that was organized by the MCH Life Course Research Network (LCRN) and funded by Health Resources and Services Administration-Maternal and Child Health Bureau (HRSA-MCHB), this volume assesses what has been learned as the LCHD field has emerged, takes stock of what we know and do not know about how health and disease develop, provides some initial guidance regarding the kinds of interventions and efforts that can be beneficial, and lays the foundation for a research agenda that identifies high-priority areas for basic, clinical, population, and translational investigations in order to strategically target resources and efforts and advance the life course health sciences. In this introductory chapter, we begin by providing a rationale for the publication of this volume, including an historical overview that traces the emergence of the LCHD field and provides evidence of a significant, but as yet incomplete, transformation in how we think about and promote health. We go on to describe the purpose, structure, and content of the volume and examine some of the challenges the evolving field must consider as it adaptively moves forward. Finally, we provide readers with information about each section and chapter in this volume, including the impressive backgrounds of the various experts who contributed substantial amounts of both time and original thinking in their roles as authors.