As compared with previous reviews, which specifically focus on CD8+TRM cells differentiation, and phenotype heterogeneity [14, 42, 43], or their roles in antitumor immunity [44, 45] or anti‐infection immunity [15, 46], in this review, we comprehensively examined the advancements in our understanding of the differentiation of CD8+TRM cells and their phenotypic heterogeneity across various tissues and disease contexts. Here, CD8A is linked to infection.