A cross section of a bundle of nerve fibers. Axons (orange) are wrapped in myelin (purple); an extension of the membrane of glial cells. Myelin has high lipid content, and acts to insulate the axons, causing them to transmit nerve impulses much faster.
Intestinal villi, finger-like projections that line-up the small intestine. They increase the surface area available for the absorption of nutrients from digested food. Magnification: when printed 10 centimetres wide.