The cytoskeleton of mammalian cells is a complex assembly of microfilaments microtubules, and intermediate filaments. The thicker fibers are the microtubules which have a diameter of approx 25 nM and an apparently hollow core; microfilaments have a diameter of 6 nM, but the third type of filaments have a diameter of approx 10 nM and are known as intermediate filaments These filamentous structures are commonly referred to as a cytoskeletal framework; however, this description is misleading, since their functions certainly include not only "skeletal properties" but also force generation and movement, cell division, uptake of materials, and transport of exocytotic and endocytotic vesicles.