This work focuses on the characterization of meso- and nanoscopic crystalline semiconductor structures by means of x-ray methods, direct scanning probe techniques and numerical simulations. Thereby structural parameters like shape, size, chemical composition and mechanical deformation have been probed. Within ensembles of nearly identical objects positional correlation plays also an important role for the scattering process. On the other hand the basic principles of self-organization are of interest. This comprises the evolution of individual objects (self-formation) as well as lateral and/or vertical correlation (self-assembling),Using high resolution x-ray diffraction one can accurately determine the local lattice parameter, which is driven by the particular chemical composition within the nanostructure. Far away from absorption edges we could show a vanishing direct influence of the chemical composition onto the x-ray scattering, which is then mainly influenced by strain. Indirectly one can, however, conclude to the chemical composition via the probed strain. This serves as essential key towards a better understanding of growth and self-organization of nanostructures.