Centrosomes are the major microtubule‐organising centres of animal cells. These small organelles participate in diverse cellular functions such as cell division, polarity, migration and signalling and are often deregulated in diseases such as cancer and microcephaly. Over the past two decades, technical advances enabled a deeper knowledge of the molecular composition and mechanisms of centrosome assembly and function. These progresses also allowed a better understanding on how the centrosome cycle is coordinated with the cell cycle to ensure that centrosomes duplicate once and only once. These discoveries together with the emergence of in vivo models of centrosome deregulation have consolidated the 100‐year‐old pioneer view of Theodor Boveri about the role of centrosome amplification (more than two centrosomes per cell) in abnormal cell division, tumorigenesis and developmental diseases such as microcephaly.

Key Concepts

• Centrosomes are made of two orthogonally oriented centrioles surrounded by the pericentriolar material.
• The ninefold symmetry of centrioles is mostly defined by the cartwheel, that is, the initial structure formed during centriole assembly made of SAS‐6 oligomers. This protein is highly evolutionarily conserved, being present in the last common ancestor of eukaryotes.
• Centrosomes are not only the main microtubule organisers of animal cells but also actin‐organising centres.
• Centriole duplication occurs only once per cell cycle and is triggered by a core module composed of PLK4‐SAS‐6‐STIL proteins. Regulation of the level of these components is critical to control centriole number in cells.
• Centrosome duplication and cell cycle progression are tightly coupled and share common regulators.
• Centrosome loss and amplification can lead to abnormal mitotic spindle formation, chromosome instability and cell cycle arrest.
• Centrosome amplification leads to tumorigenesis and microcephaly.