## 3 Imaging with Compact EUV and SXR Microscopes Based on a Laser Plasma Sources
### SXR Contact Microscopy Imaging  
The contact microscope has been used for imaging of T24 (transitional cancer cell of the urine bladder, ATCC), which was prepared in collaboration with the Institute of Nuclear Physics Krakow, Poland. The cells were grown in culture flasks (Sarstedt AG & Co., Numbrecht, Germany) in a RPMI 1640 medium (Sigma-Aldrich Sp. z.o.o, Poznan, Poland) supplemented with 10% foetal calf serum (Sigma, pH 7.4) and with 1% mixture of antibiotics (streptomycin, neomycin, and penicillin, Sigma-Aldrich Sp. z.o.o, Poznan, Poland), at 37 \({}^{\circ}\)C in 95%air/5%CO\({}_{2}\) atmosphere. After a few passages, the cells were trypsinized using 0.05% in EDTA-trypsin solution (Sigma-Aldrich Sp. z.o.o, Poznan, Poland), transferred to the Petri dishes with a PMMA photoresist inside, and cultured for 24 h. Afterwards, the cells were fixed with 3.7% paraformaldehyde solution in PBS (phosphate buffered saline, pH 7.4, Sigma-Aldrich Sp. z.o.o, Poznan, Poland). After the fixation, the cells were washed with the PBS buffer dissolved in water, and finally washed out with deionized water. Such protocol  
Figure 4: Comparison of CT 26 fibroblast cells sample acquired with optical microscope (**a**) and the EUV microscope (**b**). It is possible to recognize small features of the order of 100 nm (as indicated in red arrows) in the EUV image. The EUV image of Chrysodilimus cells (**c**) and diatoms (**d**) obtained with exposure of 100–200 EUV pulses. Features as small as 50–100 nm are visible. allows drying of the cells with no crystallization of salt on the sample surface. The contact microscope images of the T24 cell lines were acquired using 200 pulses of SXRs with exposure time of 20 s. Following exposure to the soft X-rays, the photoresist was cleaned using a 1% chloro solution (sodium hypochlorite 5.25% \(w\)/\(w\)) to remove all residues of the sample. The photoresist was then developed in methyl isobutyl ketone and isopropyl alcohol (MIBKIPA, 1:2 \(v\)/\(v\)) for 120 s. The development process results in a high resolution relief-map of the cellular structures within the photoresist, which was then viewed at high magnification by means of an atomic force microscope (AFM, NT-MDT Spectrum Instruments, Moscow, Russia). The AFM scan was made in a semi-contact mode over an area of 80 \(\times\) 80 \(\upmu\)m\({}^{2}\) with 512 pixels per line and 25 \(\times\) 25 \(\upmu\)m\({}^{2}\) with 1024 pixels per line, respectively. The micrographs of the contact microscope images of the T24 cancer cells are shown in Figure 5a,b. In these images, the overall structures of the cells, including the central dense part (nucleus), are clearly visible. Another sample used in the preliminary contact microscopy experiments was epidermal cell (Keratinocyte), as depicted in Figure 5c,d. The sample was prepared in collaboration with the Institute of Biotechnology, Warsaw University of Technology, Warsaw, Poland. The sample was cultured on PMMA photoresist in a controlled culture conditions. A Dulbecco's Modified Eagle's Culture Medium (DMEM, Sigma-Aldrich) supplemented with 1% L-glutamine, 1% penicillin/streptomycin, and 10% heat inactivated fetal bovine serum (Celbio, EuroClone S.p.A., Pero, MI, USA) was used as a culture medium. The culture medium was washed with PBS buffer solution followed by fixation and dehydration of the cells using paraformaldehyde 3.7% in phosphate buffered saline at 35 \({}^{\circ}\)C. The exposure of 200 SXR pulses, 20 s exposure time, was required to expose the PMMA photoresist and reach spatial resolution of approximately 80 nm half-pitch. The photoresist was treated with previously mentioned procedure and later scanned with AFM (AFM, NT-MDT Spectrum Instruments, Moscow, Russia) operating in semi-contact mode.