Microvilli are thin, projections on the apical surface of epithelial cells that line specific organs, such as the small intestine, large intestine, and kidney. These cells have a brush border appearance because of the finger-like protrusions. Microvilli increase the plasma membrane's surface area twenty-five-fold, allowing for greater nutrient and water absorption. Additionally, enzymes present in the microvilli can aid in the break down of absorbed nutrients. Actin microfilaments form the microvilli's internal structure. Villin and other bundling proteins like fimbrin crosslink actin and promote the formation of tightly bundled parallel arrays. These bundles orient microvilli so they project outward from the apical cell surface.