The centromere defines where on a chromosome the kinetochores assemble. Kinetochores, large protein structures, mediate chromosome segregation during mitosis and meiosis by performing three key functions. Firstly, kinetochores attach chromosomes to the microtubule spindle apparatus. Secondly, kinetochores co-ordinate microtubule dynamics to allow chromosomes to move along the spindle. Lastly, kinetochores generate the 'wait' signal which prevents anaphase onset until all the chromosomes are correctly aligned on the spindle. This signal forms part of the spindle checkpoint mechanism, a highly conserved cell cycle checkpoint which maintains the accuracy of the chromosome segregation process. This article provides a brief historical overview before focusing on some of the outstanding issues and more recent developments in the field.