Cellular life hinges on a network of hollow cables called microtubules dynamically lengthening and shortening according to the needs of the moment. During cell division, for instance, these cables latch onto chromosomes and retract—yanking chromosomes to either end of the cell to ensure that each daughter cell receives an equitable share of genetic information. In addition to regulating the dynamics of microtubules, the cell also regulates the precise timing and location of microtubule formation. There's little room for error.