Nano and micro X-ray beams are an emerging characterization tool with broad implications for semiconductor research. Here we describe how (sub)micrometer X-ray beams can be formed and used today using refractive, reflective and diffractive optics. We show that X-ray microscopy both at the nano- and microscale, is a key tool for space-resolved determination of structural (XRD) and electronic (XANES/EXAFS) properties and for chemical speciation (XRF) of nanostructured or composite materials. Selected examples will range from cluster formation to particle contaminations and dopant segregation effects, to phase separations and embedded structural domains.