The cytoskeleton is a dynamic three-dimensional structure that fills the cytoplasm of cells. The cytoskeleton is responsible for cell movement, cytokinesis, and the organization of the organelles or organelle-like structures within the cell. The major components of the cytoskeleton are the microfilaments (of actin), microtubules (of tubulin), the intermediate filament systems and a fourth group, the MinD-ParA group, that appears to be unique to bacteria.