Tissue pieces were made conductive by osmium impregnation (revised tannin-osmium method of MURAKAMI, 1974) and embedded in hydroxy ethyl methacrylate. The resin-embedded specimens were cracked and observed, with neither elimination of resin nor metal coating, in the scanning electron microscope. Using the bone marrow of the rat femur, it was shown that this resin-embedding preserved the delicate tissue-elements without undesirable dislocation and breakage and assured the effective scanning observation as high as ×10, 000 at 25kV accelerating voltage. Passage of blood cells through the sinus wall was thus clearly demonstrated.