CASP3 and neoplasm: HeLa tumor‐bearing model results showed that the intratumoral injection of NaYF4:Yb3+,Tm3+@NaGdF4:Yb3+@TiO2 (UCNPs@TiO2) core/shell nanoparticles followed by 980 nm laser irradiation achieved the substantial tumor‐growth suppression with high therapeutic efficiency/outcome (Figure 4d,e), which was further demonstrated by immunohistochemical staining for caspase 3.88