The dynamic behaviors of collective cells play a significant role in many physiological and pathological processes,e.g.,embryonic development and cancer metastasis.In this talk,theoretical models,numerical simulations,and experimental measurements are combined to investigate the dynamics of collective cells.First,we investigate how embryonic stem cells maintain their pluripotency and structural integrity during the growth of an embryonic colony.We report that a mouse embryonic stem cell colony generates a surface tension through a three-dimensional supercellular actomyosin cortex (3D-SAC) to sustain its integrity and pluripotency.Second,we study,both theoretically and experimentally,the oscillation of collective cells in a monolayer.The Drosophila amnioserosa is used as a model system,and a chemomechanically coupled dynamic vertex model is established for the molecular mechanisms and cellular interactions in an ensemble of cells.We show that the observed Drosophila amnioserosa oscillation is a biological demonstration of Hopf bifurcation,and mechanical forces could play a key regulating role.The tensile stress serves as a key activator that switches the collective oscillations on and off.In addition,the physical properties of the tissue boundary can synchronize the oscillatory intensity and polarity of all inner cells and orchestrate the spatial oscillation patterns.