The microenvironment surrounding eukaryotic cells in complex organisms is constantly evolving. Its out-of-equilibrium behaviour is due to the perpetual production and degradation of its constituents by the enclosing cells. However, state of the art in vitro cell biology studies lack the ability of recreating such dynamic behaviour without the constant rinsing of cellular medium, and hence dismantling cellular communication. To overcome this issue, I propose the development of a reactive extracellular medium with out-of-equilibrium properties. I will show you how an enzyme-based DNA program embedded in the medium, with the help of feedback loops and repression mechanisms, is capable of delivering information to living cells with temporal control. In particular, I will demonstrate how an inhomogeneous version of the program can provide positional information to cells, emulating archetypal mechanisms observed during embryo development.