I will try to illustrate the essence of non-equilibrium statistical physics, the branch of science which is not so much the study of a specific subject {\em per se}, but rather a collection of ideas and tools that work for an incredibly wide range of problems. I will exemplify some of the key insights that have emerged from the analysis of far-from-equilibrium behaviors. As in other interacting many-particle settings, the large size often plays an advantageous, rather than deleterious, role in leading to simple collective properties. I'll focus on diffusion-reaction systems and I'll also discuss a connection with non-equilibrium spin systems.