Fig. 1. The mechanism of the NIR-II optical bioimaging ^［15］，（a） the light absorption spectrum of water within 700-2 500 nm，（b） the simulation results of the NIR bio-tissue imaging via Monte Carlo method in 1 300-2 340 nm，（c） the schematic diagram of light propagation in tissue，the propagation of excited ballistic and diffused emission photons in the bio-tissue with small（left） and moderate （right） light absorption and the resulting SBRs of the fluorescence imaging

Fig. 2. All imaging equipments can be integrated into a compact open-field device or within laparoscopic and other surgical instruments for contact-free and real-time imaging^［26］.

Fig. 3. The development roadmap of 1-1.7 μm InGaAs FPA in SITP^［28］

Fig. 4. The NIR-II fluorescence imaging guided sentinel lymph node resection^［49］

Fig. 5. （a）The triple-channel NIR-II fluorescence imaging of LNs，blood vessels，and ureters on rats^［21］，（b）the hybrid NIR-II and visible fluorescence imaging of mesenteric lymph nodes and corresponding lymphatic vessels^［55］

Fig. 6. The intraoperative NIR-II/I imaging of patients with different types of liver cancer^［29］，（a） the intraoperative NIR II/I images for a nodule of liver cancer，intrahepatic metastases，and extrahepatic metastases，respectively，（b） the cross-sectional intensity distribution of NIR-II and NIR-I images in the white arrow region in （a），（c） a small intrahepatic metastasis in the right liver was successfully detected by the NIR-II imaging，as shown by the red arrow. However，the NIR-I imaging failed to detect the lesion

Fig. 7. The intraoperative fluorescence imaging and the pathological results in hepatectomy^［58］，（a–b） the enhanced CT results showed a lesion in the right liver lobe，（c–e） show the in vivo images before lesion resection，（c） was acquired in the visible light spectrum while （d） was the white-light observation using the NIR-II imager，（e） the NIR-II fluorescence was detected in the liver parenchyma and the lesion was visualized with a high contrast of 10.43，（f，g） the fluorescent margin on the resected lesion aided to achieve a complete resection，（h–i） exhibit the distribution of the NIR-II fluorescence on the lesion ex vivo，four typical specimens （①~④） were taken for pathological analyses，（j） the pathological results showed that ① was the moderately differentiated HCC，② was the moderately-poorly differentiated HCC，the fluorescent ③ and ④ were the cirrhosis

Fig. 8. Comparison of multispectral fluorescence images^［61］，（a） the vascular SBR in different spectra of each patient，（b） the mean vascular SBR of the seven patients，（c-d） the visible light and multispectral fluorescence images of cerebral vessels，（e） the fluorescence images of the enlarged view of the white rectangle in （c），three veins are distinguished in the NIR-I and NIR-II imaging while four are distinguished in the NIR-IIa and NIR-IIb imaging，（f） the cross-sectional intensity profiles，which correspond to the location and direction of white arrows in （e），respectively，d1 indicated the center distance between vessel 1 and vessel 2，which was 0.67 mm，similarly，d2 indicated the center distance between vessel 3 and vessel 4，which was 0.71 mm

Fig. 9. The intraoperative NIR-II image-assisted kidney mass resection^［65］，（a） the visible and NIR-II images of the tumor and renal parenchyma，（b） the visible and NIR-II images of the surgical margins，（d） the visible and NIR-II images of the tumor base

Fig. 10. Applications of the NIR-II imaging with ICG in microsurgery^［69］，（a） the NIR Imaging for the assessment of vascular patency during anastomosis，（b） the NIR Imaging for a thumb replantation，（c） the NIR Imaging for the avulsion injury reconstruction