APOE and Alzheimer disease: Lipidomic analyses of the postmortem human AD brain have noted changes in brain lipids during the course of the disease.66 Recent work extends these findings to include E4-associated decreases in several phospholipid species67,68 and isoform-specific microglial responses to ApoE-containing, phospholipid-rich lipoproteins.69 Although brain lipidomic profiling typically relies on tissue homogenates from preselected regions, we here leveraged MALDI MSI to simultaneously quantify multiple lipid classes across entire intact brain tissue sections.