 With the Second Law thermodynamics is able to characterize an extraordinary range of phenomena under one simple law. Remarkably, whether they are gases filling their available volumes, iron bars in contact coming to the same temperature, vinegar and oil separating, or milk mixing in your coffee, they all have an observable property in common: their entropy increases. Coupled with the First Law, the Second Law is remarkably powerful. It appears that all classical thermodynamical behavior can be derived from these two simple statements (O. Penrose 1970).