Growing up is stressful: biophysical laws of morphogenesis

Would it not be nice to understand the rules that govern how a small and round zygote reforms itself into a full blown three-dimensional and structured organism? The past decades have provided us with a wealth of knowledge about molecular mechanisms, intracellular behaviors, and tissue organization. However, we still do not know how to systematically integrate molecular mechanisms into descriptions that operate at larger scales involving higher-order structures such as the actomyosin cell cortex or an entire tissue. For development, it is the biophysical laws by which these structures deform, move, and restructure that are essential for morphogenetic rearrangements at developmental length- and time-scales. Recent years have seen the advent of systematic approaches for identifying these laws and ways to determine associated physical behaviors. Here I attempt to paint an intuitive picture of the mechanical concepts that are important for large-scale developmental rearrangements, and I briefly review the technique of laser ablation for measuring associated physical quantities and testing physical models.