All field theories are effective... but some are more effective than others. More often than not models in physics are derived by intuition, educated guesses and symmetry arguments. In this talk I will show how a careful, systematic, building of a mesoscopic model from a microscopic model uncovers important physics. I will use an example from interfacial phenomena but the same techniques can be applied to any field theory. I will also present some neat analogies between cosmology and soft matter physics.