After introducing the notion of homeostatic pressure, I will subsequently introduce dynamical equations, which exhibit fluid like behavior on time scales long compared to duplication and apoptosis times, in the vicinity of homeostatic conditions. Subsequently, I will describe stress-clamp experiments, which provide numbers on the effects of stress on cell division and apoptosis and introduce the idea of “active” tissue, which allows us to understand some aspects of experimental results. Then I will describe a dynamical transition in nematic epithelia which we predicted about ten years ago in active gels. Eventually, I will shortly give some conjectures about long time electric effects on polar tissues.

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