[en] Several experimental problems encountered in studies of the optical properties of gases and solids in the vacuum ultraviolet (VUV) and soft X-ray region were essentially overcome during the last few years. The utilization of synchrotron radiation as an intense, highly polarized continuous light source was one of the major breakthroughs. In this paper, the emphasis is placed on those experiments which have been performed during the last three years at the Deutsches Elektronen-Synchrotron DESY on molecular crystals in the excitonic region of the spectrum. Experimental results for molecular crystals formed by rare gases, atmospheric gases and simple hydrocarbon molecules are discussed. (Auth.)