Mechanisms that determine the size of plants have fascinated plant scientists of all times, however they are far from understood. An international research team led by plant scientists from VIB and Ghent University report an important breakthrough in the scientific journal The Plant Cell. They identified a protein complex that controls the transition from cell division to cell specialization. By extending the activity of the complex during leaf growth, more cells divide, giving rise to larger leaves. These insights can now be used to guide plant breeding initiatives towards higher plant productivity.