Microstructural studies were conducted on palladium specimens that were taken from ambient-temperature heavy water and elevated-temperature molten-salt electrolytic experiments. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate the surface and interior portions of these specimens. A subgrain structure could be observed by SEM on the surface along the longitudinal direction and on the surface taken from the cross section of the deuterium-charged specimen rod; the thermoelectrochemical etching process was consequently applied to the deuterium-charged specimen rod. A TEM bright field and selected area diffraction pattern technique verified that dislocation cells and subgrains exist in the deuterium-charged specimens. If cold fusion effects exist in the palladium microstructure, which consists of dislocation cells and subgrains, understanding the cold fusion phenomenon in the microstructure is necessary, and pursuant to this understanding, electrolytic experiments of a palladium rod in molten salt and of heavy water may be useful.