Molecular motions in a solid controls how fast it undergoes physical and chemical changes. We are studying two types of molecular mobility in organic glasses: surface diffusion and moisture diffusion. The method of surface grating decay is used to measure the surface molecular mobility of organic glasses. This property is of interest because crystal growth can occur orders of magnitude faster at the surface than in the bulk of organic glasses. Raman microscopy is used to measure moisture diffusion in sugar glasses. This property is of interest because the interaction with water is a major mechanism for the degradation of pharmaceutical and food products.