Using endometriotic lesions obtained from patients with severe endometriosis (n = 3), dual staining for IL-33 with cytokeratin (epithelial cell marker) (Figure 1C and Supplemental Figure 2, A–C) and vimentin (stromal cell marker) (Figure 1D and Supplemental Figure 2, D–F) revealed that IL-33 colocalizes with both stromal and epithelial cells in the lesion microenvironment. Here, VIM is linked to endometriosis.