In cell biology a centriole is a cylindrical cellular organelle composed mainly of a protein called tubulin. Centrioles are found in most eukaryotic cells. An bound pair of centrioles, surrounded by a shapeless mass of dense material, called the pericentriolar material (PCM), makes up a structure called a centrosome.
Centrioles are present in the cells of most eukaryotes, for example those of animals. However, they are absent from conifers (pinophyta), flowering plants (angiosperms) and most fungi, and are only present in the male gametes of charophytes, bryophytes, seedless vascular plants, cycads, and ginkgo.
Centrioles are typically made up of nine sets of short microtubule triplets, arranged in a cylinder. Deviations from this structure include crabs and Drosophila melanogaster embryos, with nine doublets, and Caenorhabditis elegans sperm cells and early embryos, with nine singlets.
The main function of centrioles is to produce cilia during interphase and the aster and the spindle during cell division.