Transmission electron micrograph (TEM) of the ultrastructure of the microvilli at the apical surface of the small bowel epithelium. Microvilli are finger-like membrane extensions up to 1 micrometre in length of small bowel enterocytes that greatly increase the surface area for absorption of nutrients. A core of actin filaments serve to stabilise each microvillus and their membranes are associated with enzymes for digestion of dietary peptides, fats, sugars and other lumenal contents. Magnification: x13,000 when printed at a width of 10cm.