Microvilli are tiny, finger-like projections found on the surface of certain cells, particularly in the small intestine. They increase the surface area of the cell, allowing for more efficient absorption of nutrients. Each microvillus is covered by a plasma membrane and contains a core of actin filaments, which help maintain its structure. These structures are crucial for the digestive process, as they enhance the cell's ability to take in essential substances from food. Microvilli are also present in other tissues, such as the kidneys, where they play a role in reabsorbing important molecules from urine.