In article No. 1700281, Jian Liu and co‐workers develop NIR light‐triggered release of NO from nanoparticles and demonstrate inhibition of platelet aggregation in blood samples. As the key nano‐transducer, core‐shell structured UCNPs are encapsulated with a layer of SiO2, and then covalently linked with a potent NO‐releasing donor SNAP. It is featured with highly localized breakage of chemical bonds of SNAP molecules by NIR‐UV upconversion, enabling simultaneous NO release in a light dosage‐dependent manner for cellular imaging or inhibition of platelet aggregation. This work provides a flexible and robust platform to generate cell‐signaling gas molecules trigged by NIR laser with deep tissue penetration.