## 3 Imaging with Compact EUV and SXR Microscopes Based on a Laser Plasma Sources
### SXR Full-Field Imaging  
Two examples of \"water window\" images of organic samples, acquired with the full-field SXR microscope are depicted in Figure 3. Figure 3a,b show a sample of CT-26 fibroblast from Mus musculus colon carcinoma (strain BALB/c), prepared on top of a 30 nm thick Si\({}_{3}\)N\({}_{4}\) membrane. A direct comparison between the image acquired with a traditional optical microscope (Figure 3a) and the SXR microscope image (Figure 3b), acquired with 200 SXR pulses, at a source repetition rate of 10 Hz, exposure time of 22 s, and detector (CCD) temperature of \(-\)20 \({}^{\circ}\)C, are shown. The sample was prepared with a gradual dehydration in ethanol series (final concentration 70% EtOH), without any fixation procedure. The SXR image shows improved spatial resolution due to the employment of a shorter wavelength, beyond the diffraction limit of the optical-visible light microscopes. Some internal and external structures can be distinguished due to phase contrast in the visible light microscopy images and due to the modulation in the absorption of the SXR light through the sample in the SXR images.  
Figure 3e,f show improvements in the spatial resolution. The carcinoma cells (visible light microscope--VIS, and the SXR microscope--SXR labels) with insets depicting zoomed regions indicated with dotted boxes--Figure 3g. Some external structures of the cells cannot be recognized in visible light microscope images, while they are visible in the SXR microscope with features being \(-\)60 nm in size, approaching the spatial resolution of the microscope.  
A second example consists on hippocampal neurons from E17 mouse embryos, cultured for 10 days on poly-d-lysine coated, 50 nm thick Si\({}_{3}\)N\({}_{4}\) substrates before fixation in 4% PFA in 20% sucrose PBS, followed by dehydration from 100 to 70% ethanol and air drying. The neurons were also imaged using both microscopes: visible light microscope (40\(\times\) objective, 400\(\times\) magnification)--Figure 3c, and the SXR microscope (sample to CCD magnification of 410\(\times\), exposure of 200 SXR pulses, 20 s)--Figure 3d. The comparison with the optical image (Figure 3c) shows a significant improvement of the spatial resolution employing the \"water window\" radiation. In this case, it is possible to observe  
Figure 3: CT 26 fibroblast cells. Comparison of the optical image (**a**) and detail image (**b**) with the SXR \"water window\" microscope (red square in (**a**)) that shows small features of the order of 240 nm (indicated with a red arrow). (**c**) and (**d**) show a comparison of the mouse hippocampal neuron, acquired with optical microscope (40\(\times\) objective, mag. 400\(\times\)) and SXR microscope, respectively, showing a single neuron with dendrites branching out. (**e**) and (**f**) show colon carcinoma cells images with visible light microscope and the SXR microscope, respectively, while (**g**) depicts some smallest features visible in those images, indicating features comparable to the spatial resolution of the SXR microscope.  
that the high absorption coefficient at SXR wavelengths enhances the optical contrast to the point that a barely visible neuron in Figure 2c is much better visualized in Figure 2d. In the SXR image, it is possible to distinguish the neuron and dendrites that are blurred due to inferior resolution and phase-type imaging using the optical microscope.  
Except for the CCD background removal, adjustment of their brightness, and increased contrast in the inset of Figure 3g to show the smallest observable features, the SXR images were not altered in any other way.