Microvilli play an important role in the absorption and secretion functions of cells, according to the HyperPhysics resource of the Georgia State University website. The microvilli's role is in effectively increasing the cell's surface area.
The HyperPhysics resource states that the microvilli play an especially crucial role in the human small intestine. Microvilli are attached to the collections of cells known as villi that extend from the tissue of the small intestine. They work to dramatically increase the amount of surface area available for the digestive process. The microvilli extend the surface area to such an extent that absorption can occur on an effective surface area of around 250 square meters. Any given cell can have either microvilli or cilia, which are larger slender extensions, attached to it.