The little striped zebrafish starts out as single big cell sitting on top of the yolk. During the next 3 days, cells divide and tissues move to give the fish its final shape. But how do tissues coordinate their often-complicated movements? The physical basis of tissue coordination in early zebrafish development is subject of a study by Carl-Philipp Heisenberg, Professor at the Institute of Science and Technology Austria (IST Austria) and his group, including first author and postdoc Hitoshi Morita, and colleagues at The Francis Crick Institute in London and the Max-Planck-Institute for the Physics of Complex Systems in Dresden. Until now, little has been known about how tissues coordinate their movement both temporally and spatially during development.