Centrioles are a small group of microtubules which lie close to the nucleus of a cell. They are an essential part of all animal cells. Typically, they occur in pairs, but they are not visible during regular cell activities. They become visible during their primary function: cell division.
Location of Centrioles
Centrioles in Cell Division
Once the two pairs move to each side of the cell, the centrioles get to work. During prophase, they connect themselves to chromosomes using spindle fibers. They pull the chromosomes apart until the entire cell begins to split down the middle. New nuclear membranes begin to form around the separated chromosomes, called telophase. The process is complete after the two new cells separate completely and new cell membranes form, also called cytokinesis.
Each new cell will have its own pair of centrioles, which are hidden until the new cell divides again. This is a cycle that continues, with daughter cells eventually growing and splitting into new daughter cells. Cell division is one of the true wonders of the biological world.