Location: During rest time, centrioles are found hanging around the nucleus, but when it comes time for the cell to reproduce, they are no longer visible. They are found in all animal cells and some lower plant forms.
Structure: Centrioles are made of microtubules. They are in pairs of three all around the organelle.
Function: Centrioles are for reproduction purposes. When it comes time for the cell to divide, the two centrioles found in a cell split so there are no four. They then go to opposite sides of the nucleus, connect to the chromosomes, and split the cell into four. Source: http://www.biology4kids.com/files/cell_centriole.html