Microfilaments are thin, thread-like structures made of a protein called actin. They are part of the cytoskeleton, which provides support and shape to cells. Microfilaments play a crucial role in various cellular processes, including movement, division, and maintaining the cell's structure. These filaments are involved in muscle contraction and are essential for the movement of cells, such as in amoebas that use them for crawling. Additionally, microfilaments help in the transport of materials within cells and contribute to the formation of cellular extensions like microvilli and filopodia.