We use Ascidian (sea squirt) embryos to study how embryos pattern force generation in space and time to orchestrate tissue morphogenesis. Ascidian embryos shape themselves using classical morphogenetic mechanisms like invagination, convergent extension and zippering/fusion of epithelial sheets. They do this very fast, with very few cells, under the control of well-characterized regulatory gene networks and highly conserved signaling pathways. Small, optically clear embryos, and well-developed tools for genetic perturbation and transgenesis, provide a unique opportunity to study the dynamic integration of cell fate determination, tissue polarity, and the cytomechanics of tissue morphogenesis. In previous work we have studied dynamics of endoderm invagination during gastrulation, and the dynamics of notochord invagination and elongation. Our current focus is on the dynamics of neural tube closure.