Measuring and manipulating mechanical forces during development.

Tissue deformations are a central feature of development, from early embryogenesis, growth and building the body plan to the establishment of functional organs. These deformations often result from active contractile forces generated by cells and cell collectives, and are mediated by changes in their mechanical properties. Mechanical forces drive the formation of functional organ architectures, but they also coordinate cell behaviour and fate transitions, ensuring robustness of development. Advances in microscopy, genetics and chemistry have enabled increasingly powerful tools for measuring, generating and perturbing mechanical forces. Here we discuss approaches to measure and manipulate mechanical forces with a focus on developmental processes, ranging from quantification of molecular interactions to mapping the mechanical properties of tissues. We focus on contemporary methods, and discuss the biological discoveries that these approaches have enabled. We conclude with an outlook to methodologies at the interface of physics, chemistry and biology to build an integrated understanding of tissue morphodynamics.