Cells are typically grouped into classes and types based on assumed shared features like morphology, physiological properties, and/or transcriptional states. Microglia are not excluded from this structure-to-function assumption: A branched microglial morphology is commonly associated with a surveilling function in a healthy environment, whereas reactive microglia retract their processes towards an amoeboid-like shape, typically observed under disease conditions. Extensive transcriptional profiling of microglia across development and disease progression suggests they form “signature clusters”. Still, no defined transcriptional signature to a distinct function beyond a disease cluster has been observed. This suggests that microglia are either just heterogeneous by nature or that methodological limitations have prevented further insights.