This document discusses human ageing from several perspectives. It begins by defining ageing as the accumulation of physical, psychological, and social changes that occur over time in humans. Some dimensions expand with age while others decline. Theories of ageing include both biological theories related to wear and tear on cells and tissues, as well as psychosocial theories involving disengagement, activity levels, and social support. Successful ageing consists of low disease, high physical/cognitive function, and engagement with life. The document also examines molecular aspects of ageing including telomere shortening and changes in mitochondria.