Microtubules are microscopic hollow tubes made of the proteins alpha and beta tubulin that are part of a cell's cytoskeleton, a network of protein filaments that extends throughout the cell, gives the cell shape, and keeps its organelles in place. They are responsible for various kinds of movements in all eukaryotic cells. Microtubules are involved in nucleic and cell division, organization of intracellular structure, and intracellular transport, as well as ciliary and flagellar motility.