ConspectusBiomarkers play a vital role in the regulation of life processes, especially in predicting the occurrence and development of diseases. For the early diagnosis and precise treatment of diseases, it has become necessary and significant to detect biomarkers with sensitivity, accuracy, simplicity, convenience, and even visualization. Fluorescent-probe-based techniques have been recognized as one of the most powerful tools for the sensitive detection and real time imaging of biomarkers in biological samples. However, traditional optical probes, mainly including the visible probes (400-700 nm) and the near-infrared I (NIR-I, 700-900 nm) probes, suffer from low sensitivity, poor resolution, strong absorption and scattering, and high background fluorescence, which hinder effective monitoring of biomarkers.Fortunately, the past decade has witnessed a remarkable evolution in the application fields of near-infrared II (NIR-II, 900-1700 nm) fluorescence, driven by its exceptional optical characteristics and the advancement of imaging technologies. Leveraging the superior penetration capabilities, negligible autofluorescence, and extended fluorescence emission wavelengths, NIR-II fluorescent probes significantly enhance the signal-to-noise ratio (SNR) of