Dark energy phenomenology
In recent years, a framework to capture any departures of linear growth of structure beyond the LCDM paradigm has been developed. Any given theory can be mapped into two functions of time and scale that modify the Poisson equation and the relation between the two metric potentials. I will propose a way to take this framework beyond linear growth and discuss possible contaminations from non-linearly generated pressure and anisotropic stress. If time permits, I will discuss the phenomenogy of dark energy anisotropic stress, a property that normally is considered a smoking gun for modifications of gravity.