The centrosome is the primary microtubule organizing center (MTOC) in vertebrate cells and plays an important role in orchestrating the formation of the mitotic spindle. Centrosome maturation is an early event in this process and involves a major reorganization of centrosomal material at the G2/M transition. During maturation, centrosomes undergo a dramatic increase in size and microtubule nucleating capacity. As part of this process, a number of proteins and complexes, including some that are required for microtubule nucleation and anchoring, are recruited to the centrosome while others that are required for organization of interphase microtubules and centrosome cohesion are lost (reviewed in Schatten, 2008; Raynaud-Messina and Merdes 2007).