Organically modified layered silicate was introduced into miscible poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) blends for the synthesis and characterization of polymer/clay nanocomposite through solvent casting method. As a part of our continuous efforts on the study of nanoscopic internal structures and changes of material properties caused by the presence of organically modified layered silicate, we systematically investigated the characteristic morphological changes and internal structures with scanning electron microscope (SEM) and transmission electron microscopy (TEM). Various factors such as clay concentration, thermal history, and shear history were employed to give rise to the changes of morphological and internal structures.