Light micrograph of the smooth muscle wall of a human appendix. The smooth muscle is made up of individual cells that are arranged in two perpendicular layers. The outer layer (top half of image) is cut in cross-section and therefore we see its nuclei as circles (dark blue dots) surrounded by cytoplasm (pink). The inner layer (lower half of image) is cut parallel to the direction of the smooth muscle cells, so we see their nuclei as thin lines (dark blue) parallel to its long cytoplasm (pink) fibres. Haematoxylin and eosin stained tissue section. Magnification: x200 when printed at 10 cm.