Temperature-mapping of HeLa cells on RT nanosheets. (A) From top to bottom: Bright-field image, fluorescence image of EuTTA, fluorescence image of Rh101, and the EuTTA/Rh101 ratio image on a RT nanosheet. HeLa cells were cultured on a RT nanosheet. Left, center, and right columns indicate live cells, fixed cells, and skinned cells after fixation, respectively. Dashed lines in bright-field images indicate the outlines of cells. F.I. was normalized by that of the RT nanosheet without cells. See Fig. S5. (B) Comparison of normalized F.I. for EuTTA (left) and Rh101 (middle), and the EuTTA/Rh101 ratio (right) between live cells, fixed cells, and skinned cells after fixation. Number of cells, 58, 73, and 47 for live cells, fixed cells, and skinned cells after fixation, respectively. For EuTTA and Rh101, the Steel–Dwass test was performed. For the EuTTA/Rh101 ratio, the Tukey–Kramer test was performed. ***, P < 0.001; n.s., not significant.