TREM2 and Alzheimer disease: Although a different AD mouse model was used, a large portion of Aβ plaques were surrounded by ePtdSer, as reported previously by Huang et al. (Figure 4a; Figure S7a, Supporting Information).[7] Consistent with the co‐culture and 3D brain assembloid models, the greater number of microglia gathered in the PtdSer‐rich zone (PtdSer > 5) and showed significantly higher expression levels of TREM2 (lower two white circles; Figure 4a), although the size of the Aβ plaques did not differ significantly (quantification data; Figure 4b).