The actin cytoskeleton is a network of protein filaments found in the cytoplasm of eukaryotic cells. It is primarily composed of actin, a globular protein that polymerizes to form long, thin filaments. This structure plays a crucial role in maintaining cell shape, enabling cell movement, and facilitating various cellular processes such as division and intracellular transport. Actin filaments are dynamic, constantly undergoing assembly and disassembly in response to cellular signals. They interact with other proteins, including myosin, to generate force and movement. The actin cytoskeleton is essential for processes like muscle contraction, cell motility, and the formation of cellular structures such as microvilli.