Large Scale Structures (LSS), namely the distribution of matter in the universe, are sensitive probes of all elements of our cosmological model, such as for example Dark Matter, Dark Energy and the mechanism that generates primordial perturbations. Given the high precision of future LSS data it is very important to obtain equally accurate theoretical predictions. Inhomogeneities on scales larger than about Mpc are small and can hence be described analytically. A consistent formulation of the problem requires the use of Effective Field Theory and provides highly accurate analytical predictions. These results will be useful in extracting information from upcoming cosmological surveys