A centriole in biology is a hollow cylindrical organelle found in most animal cells, and cells of fungi and algae. The walls of centrioles are composed of nine triplets of microtubules, each arranged at an angle (so when looking down the tube, one end of the triplet pair points slightly out and the other end points slightly inwards). In cells, they are usually found in pairs at a right-angle to each other, forming a centrosome. Centrioles are important in the cell division process, organising the spindle[?] upon which the chromosomes are pulled apart.