• They are found in all eukaryotic cell
• They structure is revealed only with the help of electron microscope. They are slender and unbranched tube-like structure made up of proteins called tubulin which are helically arranged
• They have an external diameter of about 20um with walls of about 5mm lips
• They are widely distributed in the cytoplasm of cells and may occur either singly or in bundles mostly occurring at the peripherium
• They can easily be broken down and reassembled in the part of the cell where they are needed

Functions of microtubules

• Provide an internal cellular skeleton (cytoskeleton)
• Provide not in cells along which  material moves
• They aid in cells division by forming spindles
• They form a frame work on which the cellulose cell wall of plant cells is laid down
• They are a major component of cilia and flagella.