Fig. 1. The first NIR-II in vivo fluorescence imaging, (a) schematic of the exchange process to form biocompatible nanotubes.,cholate (red and white balls) on SWNTs (grey) is dialyzed and eventually replaced by phospholipid–polyethylene glycol (PL–PEG), (b) photoluminescence versus excitation spectra and how peaks are redshifted after exchange, (c) the picture (left) and the in vivo NIR-II photoluminescence (right) imaging of mice^[4]

Fig. 2. Perfecting and extending NIR-II window to 900~1 880 nm，（a）the light absorption spectrum of water within 700~2 500 nm，（b-g）the simulation results of NIR bio-tissue imaging via the Monte Carlo method in 1 300~1 400 nm，1 400~1 500 nm，1 500~1 700 nm，1 700~1 880 nm，1 880~ 2 080 nm，and 2 080~2 340 nm，（h）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 fluorescence imaging^［51］

Fig. 3. NIR-II cerebrovascular mesoscopic imaging，（a）a schematic of the NIR-IIa imaging system for brain vascular imaging，（b）dynamic NIR-IIa fluorescence imaging of a control healthy mouse and a mouse with MCAO，（c）average blood perfusion measured by the NIR-II method（red）and laser Doppler blood spectroscopy（blue）^［52］

Fig. 4. Comparison of NIR-II and NIR-I microscope imaging，NIR-II imaging affords two times enhancement of SBR，（a）ex vivo microscope imaging of mouse brains at 1-hour post-injection of IR-783@BSA at both NIR-I and NIR-II windows，scale bar：50 μm，（b）cross-sectional intensity profile of NIR-I and NIR-II images at the same location^［27］

Fig. 5. NIR-II in vivo fluorescence wide-field microscopic vascular imaging beyond 1 400 nm，the comparison of 1 400-1 550 nm and the 1 500-1 700 nm 25 x cerebrovascular microscopic imaging in the mouse at the depth of（a）150 μm and（b）650 μm，scale bar：300 μm，（c）25 x microscopic imaging in 1 400-1 550 nm at different depths in the mouse brain，scale bar：100 μm^［51］

Fig. 6. NIR II-MS the second near-infrared region in vivo microscopic imaging system

Fig. 7. Real-time and high-resolution NIR-II microscopic imaging of brain vessels，（a）intravital imaging of cerebral vasculatures using QD composite particles and the comparison with the two-photon microscopy（2PM）^［16］，scale bars：left up，1 500 μm，left down，300 μm，right，200 μm，（b）in vivo NIR-II fluorescence microscopic cerebrovascular imaging of a mouse with a cranial window at the magnifications of 5 x，25 x and 70 x，scale bars：5x，25x imaging，100 μm，70x imaging，50 μm ^［57］

Fig. 8. Study of hemodynamics utilizing NIR-II fluorescence microscopic imaging and monitoring of thrombotic ischemia in the mouse brain in real-time，（a）upper：changing of locations of a randomly chosen point signal in a blood capillary in time（diameter = 4.4 µm）with a curve of position as a function of time plotted on a graph，lower：on the left is a schematic diagram illustrating the two-photon excitation induced PTI，on the right is the NIR-II fluorescence microscopic images of brain blood vessels before（i）and after（ii）PTI induction，while（iii）and（iv）are just the heat maps of（i）and（ii）respectively，（b）NIR-II fluorescence microscopic images of brain blood vessels from a mouse intravenously injected with IR-820，while images on the left are the normal brain，images on the right are the brain with MCAO ^{［54，57］}，scale bar：100 µm

Fig. 9. In vivo NIR-II microscopic tumor imaging，（a）the schematic diagram of NIR-II fluorescence microscopy system（b）two-color NIR-II fluorescence microscopic image of CT26 tumor stroma and vessel，red：CEAF-OMe（50 μM，200 μL），λ_ex/λ_em = 940/1 200~1 700 nm，green：ICG（50 μM，50 μL），λ_ex/λ_em = 730/1 000~1 700 nm，scale bar：25 μm，（c）cross-sectional intensity profile along the white dashed line in（b）^［59］

Fig. 10. In situ NIR-II fluorescence imaging of the enhanced permeability and retention（EPR）effect in tumor sites，（a）a photograph of the tumor sites on a tumor mouse used for in vivo microscopic imaging，the left is an old tumor while the right is a new one，（b）another photograph to show the microscopic imaging on tumor sites，（c）the schematic diagram to illustrate the EPR effect，（d）visualization of EPR effect in an old and new tumor at different time via NIR-II fluorescence microscopic imaging，depth = 180 μm，the scale bar indicates 100 μm^［54］

Fig. 11. Rapid unperturbed-tissue analysis for ex vivo tumor by NIR-II wide-field fluorescence microscopy，（a）the schematic diagram of rapid pathological examination of intraoperative tissues，（b）NIR-II fluorescence microscopic images and H&E staining of cancer tissues excised from tumor-bearing mice，（c）NIR-II fluorescence and brightfield images，comparing the tumor nodules resected by patients treated without or with MMP inhibitor GM6001，T = tumor tissue，N = normal tissue^［60］

Fig. 12. Diseased intestinal segment NIR-II fluorescence wide-field microscopy，NIR-II fluorescence wide-filed microscopy on diseased intestinal segment with high spatial resolution，（a）the colonic segment was placed on a coverslip，（b）a metal annulus was placed under the coverslip，（c）a photograph of the NIR-II fluorescence wide-field microscopic imaging on the colonic segment，（d）the schematic diagram to illustrate the anatomical structure of colon wall，（e）images of the serosa taken at different depths（scale bar：200 μm），（f）images of the muscularis at different depths，（g）images of mucosa and submucosa at different depths，（h）NIR-II fluorescence wide-field microscopic images of two selected lesions，（i）the two lesions with H&E staining^［61］

Fig. 13. NIR-II rat cerebral angiography，（a）in vivo NIR-II（>1 200 nm）fluorescence microscopic imaging of brain vasculature of a rat intravenously injected with AIE dots at different depths，the red arrows demonstrate a blood capillary（diameter = 9.1 μm）at the depth of 700 μm，the cross-sectional intensity profiles and full width at half maximum（FWHM）of the blood vessels which correspond to the dotted yellow lines in（a）are plotted in（b）and（c），（d）NIR-II fluorescence image of brain vasculature of rats treated with AIE dots at the depth of 150 μm in wide field of view and（e）the cross-sectional intensity profiles of the blood vessels in different sizes corresponding to the dotted yellow line in（d）^［70］

Fig. 14. High-spatial-resolution through-thin-skull cerebrovascular microscopic imaging in marmosets，（a）the schematic diagram of the microscopic imaging system of the thinned-skull marmoset，（b）5 x NIR-II fluorescence microscopic cerebrovascular image，scale bar：300 μm，（c）the plot of cortical vessel position time function，（d）the fast Fourier transformation of time-domain signals in Fig.（c），（e）the power spectral density of Fig.（c），（f）the normalized PL intensity of the feces and urine from the marmosets，（g-m）microscopic images of different depths（100-600 μm）of cerebral blood vessels of the thinned-skull marmoset，scale bar：100 μm，（n）the analysis of the vessel at the depth of 200 μm^［71］

Fig. 15. Through-thinned-skull cortical blood flow monitoring and observation of the PTI induced thrombosis in marmosets，（a）25 x microscopic images of the cerebrovascular system and six sample blood vessels，scale bar：100 μm，（b）the plot of the time，position and distance of the fluorescent point signal in the blood vessel，（c）the average blood flow of the 6 vessels in Fig.（a），（d）the schematic of PTI induction by 532 nm laser excitation，（e）NIR-II fluorescence microscopic image of cerebral blood vessels before PTI induction，scale bar：100 μm，（f）NIR-II fluorescence microscopic image of cerebral blood vessels after PTI induction，scale bar：100 μm，（g）3D NIR-II fluorescence intensity distribution in the illuminated area before PTI induction，（h）the 3D NIR-II fluorescence intensity distribution of the illuminated area after PTI induction，the white arrows represent the flow direction before and after PTI induction，PTI causes a change in the direction of blood flow ^［71］

Fig. 16. NIR-II fluorescence wide-field microscopic imaging of cerebral vessels in rhesus monkeys，（a）NIR-II fluorescence wide-field microscopy system suitable for large animals，（b）3 x cerebrovascular microscopic image，（c）25 x cerebrovascular microscopic image，（d）blood flow velocity of the 3 sampling vessels，（e）the tracking frame display of the fluorescent signal in the capillary，picture on the right marks the tracking position，（f）the plot of fluorescent position as a function of time，scale bars in（b），（c）and（d）：100 µm，scale bars in（e）：50 µm^［74］

Fig. 17. Rhesus arteriovenous measurement and heart pulse calculation，（a）NIR-II fluorescence wide-field cerebrovascular microscopic image of blood flow direction and arteriovenous measurement，depth = 180 μm，scale bar：100 μm，（b）NIR-II fluorescence wide-field microscopic images of cerebral blood vessels of the rhesus macaque and Gaussian fitting graph of heart pulse period，depth = 130 μm，scale bars：100 μm^［74］