The cytoskeleton is the three-dimensional scaffolding present in eukaryotic cells. The structure functions similarly to both the muscles and skeleton of animals in that it provides support and causes movement. Its structure is made from three primary types of fibers, known as microfilaments, microtubules and intermediate filaments.
The cell's three primary fibers perform different functions. Microfilaments are associated with muscle and cellular movements. Microtubules play a role in the shape of a cell, and they serve as guides for many of the cell’s organelles to move along. Indeterminate filaments provide the tensile strength of the cell, keeping it from bursting as the internal pressure rises.
While the most well-known difference between prokaryotic cells and eukaryotic cells is the presence of a nucleus in the latter, the cytoskeleton is another important difference between the two types of cells. The development of the cytoskeleton was an important evolutionary adaptation that allowed eukaryotic cells to thrive. When compared to the relatively simple cells of prokaryotic organisms, eukaryotic organisms have an incredibly wide diversity of cell types.
Without a cytoskeleton, eukaryotic cells would lack the stable structure on which they depend. In such hypothetical cells, the various organelles would not be able to move as well, and they may float into poor positions within the cells.