## 1 Introduction and Previous Achievements
The compact sources are also being widely used for the purpose of high spatial resolution imaging in the EUV/SXR range. An SXR source, emitting at \(\lambda\) = 2.88 nm, based on a liquid jet nitrogen target, was employed recently for microscopy in the 'water-window' range with a sub-50 nm spatial resolution, but this system presents very complicated hardware [15]. Another nano-imaging technique is represented by the employment of compact high order harmonic generation (HHG) sources for sub-100 nm spatial resolution [16; 17]. The HHG systems, however, require a femtosecond laser as a driver for HHG process. Also, typical HHG conversion efficiency (\(\sim\)10\({}^{-6}\)-10\({}^{-4}\)) often results in long exposures or does not allow a proper reconstruction of the image. Ptychographic techniques usually based on employment of hard X-ray beams are also possible, providing a very high spatial resolution, but they are extensively time consuming [18]. Imaging in the EUV range can be used to analyze very thin samples, nanofilms, and nanostructures. That is because the EUV radiation is absorbed by solid materials with thicknesses of the order of \(\sim\)100 nm [19] and by gaseous materials with thicknesses of the order of a few millimetres [20]. It was demonstrated that the radiation from a capillary discharge laser operating at a wavelength of \(\lambda\) = 46.9 nm EUV can obtain images with a spatial resolution better than 55 nm [21; 22], and that the spatial resolution of holographic images employing the same wavelength, can be improved up to sub-50 nm [23]. A solid-state target based table top EUV laser, emitting 13.2 nm wavelength radiation from Ni-like Cd ions, was employed for imaging with a sub-38 nm spatial resolution [24]. Using a xenon gas discharge source, a sub-100 nm zone-plate based EUV microscope with zooming was demonstrated. This system combines Schwarzschild objective and a zone plate for second stage magnification [25]. Very nice results were also recently demonstrated by [PERSON] et al. [26], using a liquid nitrogen target based system and a 1.3 kHz repetition rate Nd:YAG laser to record images of biological samples and nanostructures with half-pitch spatial resolution of 40-50 nm. The only drawbacks are that it is a quite complicated system and it is larger than other sources. Another interesting and already well established technique for obtaining high resolution images of samples is a projection imaging called contact microscopy. This method uses EUV and SXR radiation transmitted through the sample to expose a high-resolution photoresist underneath, being in contact with the sample. Using this method, first imprints of human blood platelets [27], fibroblasts [28], diatoms [29], and hydrated biological cells [30] were obtained. Since there is no ideal solution for the source at the moment, it is necessary to find a good compromise in desktop SXR/EUV imaging systems, between the performance--namely, high photon flux; possibility to obtain high spatial resolution images with low exposure time; and the complexity, size, cost of these setups, which is still the main limitation of short wavelength photon-based microscopes disallowing their wide-spread. Some of these problems can be addressed employing double stream gas puff target laser plasma sources for microscopy purposes. Such a source, which has been developed initially for EUV metrology applications in the frame of MEDEA+ project [31], was also recently used for surface modification of polymers for biocompatibility improvement [32] or for radiobiology applications [33]. The double stream gas puff target sources, coupled with zone plates (FZPs) optics or as illumination sources for contact microscopy, represent a very useful technique for lab-scale analysis in order to perform high spatial resolution imaging by using short wavelength radiations. Thus, in this article, we would like to present our recent activities related to the development and possible applications of three simple and compact SXR/EUV microscopes, capable of resolving 50-80 nm features.