Fluorescence imaging plays a pivotal role in the study of biological processes, and cell -permeable fluorogenic dyes are crucial to visualize intracellular structures with high specificity. Polymethine dyes are vitally important fluorophores in singlemolecule localization microscopy and in vivo imaging, but their use in live cells has been limited by high background fluorescence and low membrane permeability. In this review, we summarize recent advances in the development of fluorogenic polymethine dyes via intramolecular cyclization. Finally, we offer an outlook on the prospects of fluorogenic polymethine dyes for bioimaging.