Nucleic acid mimics of fluorescent proteins can be valuable tools to locate and image functional biomolecules in cells. Stacking between the internal G-quartet, formed in the mimics, and the exogenous fluorophore probes constitutes the basis for fluorescence emission. The precision of recognition depends upon probes selectively targeting the specific G-quadruplex in the mimics. However, the design of probes recognizing a G-quadruplex with high selectivity in vitro and in vivo remains a challenge. Through structure-based screening and optimization, we identified a light-up fluorescent probe, 9CI that selectively recognizes c-MYC Pu22 G-quadruplex both in vitro and ex vivo. Upon binding, the biocompatible probe emits both blue and green fluorescence with the excitation at 405 nm. With 9CI and c-MYC Pu22 G-quadruplex complex as the fluorescent response core, a DNA mimic of fluorescent proteins was