At first, an embryo has no front or back, head or tail. It’, s a simple sphere of cells. But soon enough, the smooth clump begins to change. Fluid pools in the middle of the sphere. Cells flow like honey to take up their positions in the future body. Sheets of cells fold origami-style, building a heart, a gut, a brain. None of this could happen without forces that squeeze, bend and tug the growing animal into shape. Even when it reaches adulthood, its cells will continue to respond to pushing and pulling —,by each other and from the environment. Yet the manner in which bodies and tissues take form remains “, one of the most important, and still poorly understood, questions of our time”, , says developmental biologist Amy Shyer, who studies morphogenesis at the Rockefeller University in New York City. For decades, biologists have focused on the ways in which genes and other biomolecules shape bodies, mainly because the tools to analyse these signals are readily available and always improving. Mechanical forces have received much less attention.