In this high magnification EM, many of the vesicles, which are lysosomes (L), are football-shaped with a dark band in the center. The eosinophil is unusual in that it fills it lysosomes with such highly concentrated enzymes that they form crystals. These appear as the dark bands. The eosinophil exocytoses its lysosomes to destroy parasitic worms, such as helminths. A thin section through the nucleus is present at the left. Other membranous vesicular structures are likely part of the ER or Golgi.