## 3 Results
Figure 3: Stitched images (20\(\times\) objective, column 1 + 3) and created images (50\(\times\) objective, column 2 + 4) of the unstained sample; modes: brightfield **(1a,3a)**, darkfield **(1b,3b)**, polarization **(1c,1d,3c,3d)**, reflectance spectroscopy **(2a,2b,4a,4b)**, Raman spectroscopy **(2c,2d,4c,4d)**; photographs: 41 \(\times\) 45 **(1a–d)**, 3 \(\times\) 3 **(3a–d)**; spectra: 37 \(\times\) 31 **(2a–d)**, 61 \(\times\) 41 **(4a–d)**; travel range: 7200 \(\upmu\)m \(\times\) 7200 \(\upmu\)m **(1a–d, 2a–d)**, scanning area: 584 \(\upmu\)m \(\times\) 438 \(\upmu\)m **(3a–d)**, 305 \(\upmu\)m \(\times\) 205 \(\upmu\)m **(4a–d)** abbreviations: AB: air bubbles, BV: blood vessel, TF: tissue fold (see text for details). Columns 1 and 2 show the images resulted from the global scan. The local scan's results are shown in columns 3 and 4. The columns with even numbers contain created images based on the evaluation of spectra, while column number 1 and 3 show stitched photographs. Information regarding the number of photographs or spectra and the travel range or scanning area of each image are provided in the figure caption of Figure 3.  
Image 1a of Figure 3 is the brightfield-microscopic image of the unstained sample's cerebral hemisphere. In comparison to Figure 2(2a), photographs were taken with the 20\(\times\) objective and a higher resolution, consequently. Figure 3(1b) is the stitched image of the same tissue section, obtained with the darkfield mode. While darkfield microscopy highlights GM bright, the same morphological structure appears dark in brightfield images. Another modality that highlights WM is polarized light microscopy. WM shines bright in Figure 3(1c), while the other parts of the image are dark. A qualitative color-coded differentiation of the WM is obtained by polarization microscopy with the activated WWC (Figure 3(1d)). While the internal capsule is highlighted in orange, the majority of the corpus callosum is colored in blue. The bright green segment (red circle) at the lower right part of the tissue, which is also visible in the previously mentioned images, could be identified as an artefact that does not belong to the brain section. The local scan's stitched images in column 3 (Figure 3(3a-d)) display the area of the blue frame in column 1 (Figure 3(1a-d)) in an enlarged image. The smaller area within Figure 3(3a) (purple frame) represents the local scan's area, where spectra were acquired. This smaller ROI comprises a boundary between cortex (GM) and corpus callosum (WM). Moreover, three landmarks for further data evaluation were determined. These include three air bubbles (AB) in the lower-left corner, a tissue fold (TF) in the center, and a blood vessel (BV) in the lower-right corner. Especially the air bubbles and the tissue fold can be identified in the created images based on reflectance spectra in the VIS (Figure 3(4a)) and NIR (Figure 3(4b)) region. Figure 3(4a) shows the reflectivity of the tissue sample at 750 nm (R\({}_{750}\)). The qualitative reflectance spectra in the VIS region are illustrated in Figure 4a. Besides the reflectance spectra of GM and WM, the reflectance spectrum of OCT is shown as well. Since the tissue was embedded in transparent OCT, OCT still surrounds the cryosection and consequently coats the microscope slide (see Figure 2(2a)). Although OCT is a side component within this proof-of-concept, OCT affects the spectral evaluation of the global scans. This is shown in Figure 3(2a). Compared to the few pixels located at the lateral ventricle and the single pixel of the 3 rd ventricle that are yellow, the OCT area is rather orange. This confirms that OCT reduces the intensity of the backscattered light compared to  
Figure 4: Reflectance spectra (averaging over 9 spectra) of white matter (WM), grey matter (GM) and optimal cutting temperature compound (OCT) in the (**a**) VIS spectral region, (**b**) NIR spectral region. the reflectivity of the gold-coated slide without tissue sample. However, reflectivity at OCT is higher than the reflectivity at WM and GM.