In a recent study conducted by the author, microcrystallites were observed to exist in amorphous, short range ordered, structures of several metallic glasses. The observation is based on X-Ray Diffraction (XRD) and Electron Diffraction (ED) and Transmission Electron Microscopy (TEM). The data from the X-ray diffraction shows that the metallic glasses have typical amorphous structures. However, the data from the Electron Diffraction indicates that the metallic glasses possess polycrystalline structures. This discrepancy between the XRD and ED data can be interpreted and explained by diffraction theory [1,2] with the aid of Transmission Electron Microscopy. In fact results in the recent work show that with a mathematical relationship originally derived by Sherrer , one can determine the boundary line between microcrystallites in amorphous, short range ordered, structures and crystalline, long range ordered, structures. The boundary line of microcrystallites is defined with the aid of Transmission Electron Microscopy in which the size of subgrains, of the metallic glasses was determined from the mathematical relationship.