Toluidine blue staining, TEM of a macrophage, and Energy-dispersive spectroscopy. Toluidine blue staining shows a blood vessel and macrophages in a lymph node (A). TEM of a macrophage (C, D). High-power images revealed small, black granules in the macrophages. The granules of approximately 10 nm in diameter concentrated in the phagosomes with a neighboring mitochondria that did not contain granules inside (shown at the lower left corner of the panel C). There were also very few granules in the surrounding cellular components (C). Energy-dispersive spectroscopy of TEM. The arrow shows a Si (silicate) peak (B).