This book aims to reflect critically on a great deal of HCI research conducted with or concerned about older adults and aging with the goal of sparking future development of the field. To that end, the book offers a critical literature review, which is informed by more than a decade of the author’s own empirical work,  of 30 years of research in HCI and related areas, including STS, sociology, the psychology of aging, and gerontology. Four key aspects are addressed: (1) conceptualization of older adults, aging, and technology, (2) progress in knowledge generation in HCI and aging, (3) conducting research methods with older adults, and (4) designing technologies for aging. To accomplish this, the book starts by considering the diversity and intersectionality of the older adult population of technology users and its implications for effectively applying HCI research methodologies. It critiques the tendency within HCI studies of solely conceptualizing aging as a problem, one that has a technological solution, and preoccupation with user deficits related to health and age-related declines in functional abilities. The book proposes a significant need for a horizontal body of knowledge in the field that is stymied by individuated development practices that start from scratch with their considerations of the older adult population for each new technology or application. This book calls on researchers to consider novel techniques without overlooking the need to deepen and widen a transversal knowledge base that helps the field progress further and produce technologies that ultimately better serve all users.