Sip a glass of wine, and you will notice liquid continuously weeping down the wetted side of the glass. Little did he realize that the same effect, later named the Marangoni effect, might also shape how embryos develop. Researchers now increasingly appreciate the role of mechanical forces in biology: forces that push and pull tissues in response to their material properties, steering growth and development in ways that genes cannot. The task now is to understand the interplay of causes, where genes and physics somehow act hand in hand to sculpt organisms. Grow With the FlowMechanical models of embryo and tissue growth are not new, but biologists long lacked ways of testing these ideas.