The centrosome is a fascinating place that marks the very center of the cell. It functions in the maintenance of cytoplasmic architecture through the nucleation and organization of microtubule arrays in interphase and mitotic cells. Centrosomes contain a pair of centrioles that embody structural features that are regular and ordered, yet highly asymmetric. Cells count from one to two by duplicating their centrosome during S phase of the cell cycle. Uncoupling of the centrosome and cell cycles has profound consequences for chromosomal instability and the origin of malignant tumors. Work in our laboratory focuses on the role of the protein centrin in the molecular and structural basis for centrosome duplication in normal cells, during development and in cancer.