Microglia, far from being simply ‘brain glue’, play an important role as the brain’s resident immune cells. Their roles include phagocytic clearance of debris, pruning of synapses, and possibly even contributing to synaptic activity, being of critical importance from early development to ageing. Despite being such long-lived cells, microglia have been relatively understudied for their role in the ageing process. Reliably identifying aged microglia has proven challenging, not least due to the diversity of cell populations, and the limitations of available models, further complicated by differences between human and rodent cells.