Novel nitric oxide (NO) responsive monomers (NAPMA and APUEMA) containing o-phenylenediamine functional groups have been polymerized to form NO-responsive macromolecular chains as truly biomimetic polymers. Upon exposure to NO - a ubiquitous cellular signaling molecule - the NAPMA- and APUEMA-labeled thermoresponsive copolymers exhibited substantial changes in solubility, clearly characterized by tuneable LCST behavior, thereby inducing self-assembly into nanoparticulate structures. Moreover, the NO-triggered self-assembly process in combination with environmentally sensitive fluorescence dyes could be employed to detect and image endogenous NO. NO problem: Polymerization of NO-responsive monomers containing o-phenylenediamine functional groups has led to the formation of NO-responsive macromolecular chains that act as truly biomimetic polymers. Exposure to NO results in the thermoresponsive copolymers undergoing self-assembly into micellar structures (see example). The NO-triggered self-assembly process with turn on fluorescence was further used to image endogenous NO.