Fig. 2.

a) The lymph node adhered to the coverslip was placed on a metal ring-like base under the microscope. b) The schematic diagram of the imaging system and LN structure. c) NIR-II microscopic images of LNs (scale bar: 50 ​μm). d) The measurement of the width of subcapsular sinus. e) H&E staining of the harvested LN (scale bar: 100 ​μm). f) The enlarged subcapsular sinus. g) The comparison of the mean width of subcapsular sinus by H&E staining and NIR-II fluorescence optical sectioning. All values are mean ​± ​S.E.M (standard error of mean) (n ​= ​6). ns, not significant. h) NIR-II microscopic images of the cortexes in the LNs (scale bar: 50 ​μm). i) The schematic diagram of two fates of NPs in LN.