Cells divide into two identical cells that then divide in turn, meaning that any tissue can grow exponentially. But the moment comes when some of them have to develop into specialized cells. On the back of a fly, for example, a cell must know that when it splits, it will give birth to two different cells: a hair and a neuron. How do these asymmetric divisions function? To answer this question, researchers have conducted an in-depth analysis of the asymmetric stem cells division that decide the fate of a fly’s cells and a fish’s neurons.