Human ageing is not solely the biological process of senescence-the gradual deterioration of bodily functions that increases the risk for morbidity and mortality after maturation. Human ageing is embedded in social contexts and is shaped by social factors. We grow old within a social network of partners, family members, and friends. In many countries, we count on old age pensions as well as health and social care services. And we have explicit and implicit assumptions about older people (as a social group), growing old (as a developmental process), and being old (as part of the life course). These assumptions, expectations, and beliefs shape human ageing, as well. We often speak about older people in general (and not about different individuals), about "the" process of ageing (and not about the multiple, unique courses which exist), and about old age as a uniform stage at the end of life (and not about the diverse and heterogeneous living situations of older people). As soon as we neglect the differences between individuals, we over-generalise and treat older people, ageing, and old age in a stereotypical manner. This stereotypical construction of older people, ageing, and old age is called "ageism." Ageism is ubiquitous: It is in our perception of older people and in our actions towards older people. We even look at ourselves as ageing persons through the lens of ageism. Most often, we are not aware of our ageist perceptions and behaviours. Ageism is prevalent in different domains of life: at work, in public spaces, in shops, and in doctors' offices. Elements of ageism can be found in individuals' behaviour, in organizational regulations, and in cultural values. Ageism is often negative and it