Actin filaments, also known as microfilaments, are thin protein fibers found in the cytoskeleton of eukaryotic cells. They are primarily composed of a protein called actin, which plays a crucial role in maintaining cell shape, enabling movement, and facilitating cell division. Actin filaments are dynamic structures that can rapidly grow and shrink, allowing cells to adapt to their environment. These filaments are involved in various cellular processes, including muscle contraction, where they interact with myosin to produce movement. Additionally, actin filaments contribute to the formation of cellular structures like microvilli and are essential for processes such as cell motility and cytokinesis.