How does fine dust aggregate into building blocks that ultimately form entire planets like our Earth? A research team led by the University of Bern, with the participation of ETH Zurich, the University of Zurich and the National Center of Competence in Research (NCCR) PlanetS has provided the first experimental evidence—obtained during parabolic flights in zero gravity—that a key physical process, known as shear-flow instability, actually occurs under conditions similar to those in planet formation regions. The study thus addresses an important gap in our understanding of the very first steps of planet formation.