Don't get "villi" and "microvilli" confused. There is a size difference amounting to several orders of magnitude. Villi are grossly visible structures, easily seen with the naked eye. They may be several millimeters long. The microvilli are no more than about 100 microns in length and perhaps 10 microns in diameter, just barely visible in a good light microscope. Microvilli are found as apical membrane specializations of individual cells; those cells cover the surfaces of the villi.