While cognitive problems have long been associated with ageing, dementia is a relatively new concept. ‘The challenge of dementia’ shows how our understanding of it was shaped by research in the late 19th and early 20th centuries. Dementia often first appears as short-term memory failure, but symptoms vary depending on the type and the regions of the brain affected. The hippocampus is often implicated, as are synaptic failures that lead to cell death. Despite a rapidly ageing population, dementia research is underfunded. Research presents challenges for scientists, including obtaining brain samples and addressing the complex processes of neurodegeneration. Dementia does not just affect the elderly.