CD8A and digestive system cancer: Critically, the heterogeneity of CD8+ CTLs within the tumor could be visualized by using these two probes to show that CD8+ CTLs were more distributed in the outer region of colon tumors than in the inner region (Figure 10A).[207] Thus, NIR‐II fluorescence molecular imaging offers visualization, real‐time monitoring, and assessment of target sites of the immune checkpoint PD‐L1 in tumors.