We study how embryos integrate biochemical signaling, cytoskeletal dynamics and cell mechanics to orchestrate complex cell and tissue behaviors. We combine live imaging, genetic perturbations, biophysical analysis, and computer simulations to address questions in three main areas: Dynamic control of self-organized actomyosin contractility, cell polarization in C. elegans, and tissue morphogenesis in ascidians The forces that shape embryonic cells and tissues are produced by dynamic contractile networks of actin filaments, myosin motors and cross-linking proteins. The big challenge is to understand how embryonic cells remodel these networks by tuning network assembly, architecture and motor activity to do a sequence of different jobs – to polarize, move, change shape and divide. To address this challenge, we combine in vivo studies in C. elegans with computer simulations, focusing on three specific examples: the long range flows that polarize cells, self assembly of the contractile ring during cytokinesis, and dynamic control of pulsatile contractions that coordinate cell shape change and rearrangements during morphogenesis. We also use C. elegans embryos as a model system to explore how cells form and stabilize polarity in response to transient polarizing cues. In recent years, we (and others) have uncovered a network of biochemical and mechanical interactions involving conserved PAR polarity proteins, small Rho family GTPases, and the actomyosin cytoskeleton, that do this job. We combine single molecule imaging, genetic manipulations and biophysical analysis to characterize key elements of this “mechanochemical circuit”, and to probe the fundamental design principles that allow this circuit to do it’s job in such an extraordinarily robust way. Finally, we use ascidians (“sea squirts”) as a simple model system to study how embryos organize force production in space and time to shape tissues and organs. Ascidians make the many of the same structures that we do – e.g. a notochord, a simple gut and a neural tube, but they do so with very few (tens of) cells, in small optically clear embryos, that are highly accessible to genetic, pharmacological and physical manipulations. We currently focus on neural tube closure. Combining experiments with computer simulations, we ask how embryos use tissue-specific gene expression and conserved pathways for planar and apico-basal polarity to pattern actomyosin contractility in space and time to shape and close the neural tube.