One more significant aspect of modern microscopy is the quantitative interpretation of the images in terms of the microstructure of the object. Although most microsco-pes include or can be combined with powerful image processing systems, the interpretation of the contrast is still the main problem. On the other hand, reliable micromorphological information could be easily obtained from a set of thin flat cross sections which reveal only density information, from which case accurate two- and three-dimensional numerical parameters of the internal microstructure could be calculated.

Considering existing microscopical techniques, one can find that non-destructive information from the internal structure of an object in natural conditions can be obtained by transmission X-ray microscopy. Combination of X-ray transmission technique with tomographical reconstruction allows getting three-dimensional information about the internal microstructure [1-3]. In this case any internal area can be reconstructed as a set of flat cross sections which can be used to analyze the two- and three-dimensional morphological parameters [4]. For X-ray methods the contrast in the images is a mixed combination of density and compositional information. In some cases the compositional information can be separated from the density information [5]. Recently there has been a significant improvement in the development of X-ray microscopes using synchrotron sources. However, these facilities are rather complicated and expensive and are not accessible for most researchers. On the other hand, the last few years have shown also a steady improvement in X-ray source technology so that now inexpensive compact sealed X-ray microfocus tubes can be produced with a very long lifetime. Because these sources emit polychromatic radiation one cannot use X-ray lenses for optical magnification. However, since the source spot size is small one can project the object over a large distance to the detector so as to obtain a geometrical magnification. In that case spatial resolution is limited by the X-ray spot size. At this moment, the attainable spot size in of the order of 8-10 micrometer but with the steady technological improvement one can expect submicron X-ray sources in the coming years.

(Conclusions) The state of the art in X-ray technology and computer sciences allowed developing an inexpensive compact instrument for three-dimensional non-destructive micro-scopy. The technique does not require any specimen preparation. During the investi-gation the object can stay in environmental or special conditions. Even living objects can be investigated. At present the resolution is somewhat better than 10 micrometer and can be used for objects of centimeter size. Further progress in X-ray sources and cameras allows expecting improvements in spatial resolution and avoiding limitations in object size.