In the last decade, motivated by advances in cell biology, theoretical studies of
the cell tissue as active matter have emerged as a new area in soft matter physics. This
article reviews recent theoretical progresses based on the active network (AN) model of cell
tissue. In the mesoscopic scale, the non-equilibrium dynamics of cell tissue is mainly driven
by the self-propulsion of cells and non-propulsion activities, like active contractility or cellular
tension/volume oscillation. AN models of self-propelled cells can reproduce complex dynamics
of cell tissue in vivio, such as activity/adhesion driven solid-liquid transition, flocking and
active turbulence. The AN model incorporating cellular tension fluctuation can also simulate
the cell volume oscillation waves in embryo of Drosophila, and predict the fluctuation-driven
solid-liquid transition of cell tissue. The structural phase transition and density fluctuation
of cell tissue were also studied by using AN models, which deepens our understanding of this
unique non-equilibrium soft matter system.
