Microtubules

Microtubules are a component of the cytoskeleton in cells. They are made up of a globular protein called tubulin and are roughly 25 nm in diameter.

Microtubules have multiple functions within a cell. The rigidity of microtubules allows them to maintain the cell's shape. They also control movement of the cell as well as movement of intracellular organelles. During mitosis, microtubules form the mitotic spindle required to separate the chromosomes.