In this chapter, we discuss how social and biological studies of ageing can converge to provide a meaningful framework for progress in both understanding ageing and dealing with it in a positive manner. We start by discussing the meaning of the term 'ageing' and how it is in part defined by social context, and then, how psychosocial factors have an impact on both perception and the biological reality of ageing. From a theoretical perspective, we assess how ageing might have evolved, and how it is measured. The biological impacts of ageing are then described, moving from individual cells through tissues to major organ systems (immune, cardiovascular and nervous systems) (see Figure 2.1). What causes individual cells of the body to age is dealt with at both a cellular and molecular level, and we further discuss how studies of both extremely long-lived and short-lived humans have contributed significantly not only to our understanding of the biological processes of ageing, but also to the possibility of developing therapies to deal with the problems that cause greatest loss of quality of life in older age. We end by assessing the ethical case for intervening in those biological processes underpinning the development of those illnesses that so undermine health in later life.