Jonathan Pines is Senior Group Leader at the Gurdon Institute in Cambridge. He has made key discoveries in the cell cycle field, many of which have opened up new avenues of research. He cloned the original ‘cyclin’ as a PhD student with Tim Hunt and demonstrated that it had mitosis-promoting activity. This dsicovery was essential to the subsequent cloning of Xenopus cyclins and kept the Hunt lab at the forefront of cyclin research. Subsequently he cloned and characterised the first human cyclins with Tony Hunter. This was crucial to recognising that cyclins are conserved critical regulators of cell division. He provided the first evidence that there is a family of cyclin-dependent kinases by identifying the second Cdk, Cdk2, and identified the first link between cyclins and oncoproteins by showing that cyclin A bound to adenovirus E1A, thus linking cyclins to the E2F/Retinoblastoma pathway. These discoveries sparked intensive efforts by many laboratories. In leading his own group he has shown the importance of analysing both the spatial and temporal control of the cell cycle, pioneering fluorescence time-lapse microscopy to study the cell cycle. After discovering that mitotic cyclins localise to different sub-cellular compartments he showed how they dynamically specify their localisation. Recently, he discovered that the mitotic kinase, cyclin B1-Cdk1 is activated on centrosomes, and thereby prompted considerable interest in the role of the centrosome in initiating mitosis. He has developed a novel live-cell assay for proteolysis and uncovered new mechanisms by which cells control mitosis. His analyses have shown how ubiquitin-mediated proteolysis coordinates chromosome congression with cytokinesis and mitotic exit by degrading specific proteins at specific times. He has radically altered our understanding of the control of mitosis.