Pericentriolar material (PCM, sometimes also called pericent matrix) is a highly structured,[1] dense mass of protein which makes up the part of the animal centrosome that surrounds the two centrioles.
The PCM contains proteins responsible for microtubule nucleation and anchoring[2] including γ-tubulin, pericentrin and ninein.
[citation needed] Some PCM proteins are organized such that one end of the protein is found near the centriole and the other end is farther away from the centriole.
After cell division, the PCM size is reduced in a process named centrosome reduction.
[3] During the G2 phase of the cell cycle, the PCM grows in size in a process named centrosome maturation.