During cell division the 23 chromosomes must be first copied and later delivered to two newly forming daughter cells. At least in healthy cells, the result is astonishingly flawless, and no chromosome is ever lost. A multilayered protein structure called the kinetochore executes the chromosome delivery program. In a highly interdisciplinary collaborative tour-de-force, the groups of Andrea Musacchio and Stefan Raunser at the Max Planck Institute of Molecular Physiology studied the outermost layer of this structure, the kinetochore corona. They revealed the structural organization of the corona’s main building block, the RZZ complex, and deciphered the mechanism of corona assembly.