The term centrosome was intro­duced by T.Boveri in 1888. He de­scribed the organelle as a clear cyto­plasmic area closely placed to inter­phase nucleus. Centrosome is a nonmembranous cell organelle found in all animal cells and flagellated plant cells like motile algae and motile sex cells of some primitive plants. During cell division, it gives rise to a pair of centrioles, and hence, is called diplo­some. Centrioles are cylindrical structures, which vary from 0.3-07u in length and 0.15-0.25u in diameter. The centrioles occur in pairs at right angles to one another near one pole of the di­viding nucleus.

Each centriole consists of nine triplet fibres equally spaced around an imaginary axis. Each triplet consists of three second­ary fibres or tubules which make a 40° angle with the radius of the cylinder. All these tubules are interconnected by linkers which joins tubule one of one triplet with tubule three of the next triplet. All the tubules remain enclosed in a matrix. They exhibit the same arrangement as the basal bodies of cilia and flagella. DNA and RNA are said to be present in centrioles.

During cell division, the centrioles separate and migrate to opposite poles of a cell and function as centres for spindle fibre organisation. Centrioles are also associated with the organisa­tion and development of cilia and flagella. They move to the periphery of the cell and act as basal bodies. Preex­isting centrioles can replicate to form two pairs, one for each daughter cell.