Microglia are the brain’s own immune cells, acting both as soldiers and caretakers. You could think of them as the Pac Man of the brain; they help protect brain health by engulfing harmful substances, clearing away dead cells, and removing waste. In brain diseases such as Alzheimer’s disease, microglia play an especially important role. Many genetic risk factors for Alzheimer’s are linked to these cells, placing microglia at the center of brain inflammation. Healthy brain function depends on careful communication between different cell types, but in disease this communication can become disrupted. To better understand how microglia change and contribute to disease, advanced experimental models have been developed, including microglia‑like cells generated from human blood and transplantation into mouse brains. These approaches allow the study of microglial behaviour and interactions with other brain cells and may open new paths toward treatments targeting the brain’s immune system.