Like emergency workers rushing to a disaster scene, cells called microglia speed to places where the brain has been injured, to contain the damage by ‘eating up’ any cellular debris and dead or dying neurons. Scientists at the European Molecular Biology Laboratory (EMBL) in Heidelberg, Germany, have now discovered exactly how microglia detect the site of injury, thanks to a relay of molecular signals. Their work, published today in Developmental Cell, paves the way for new medical approaches to conditions where microglia’s ability to locate hazardous cells and material within the brain is compromised.