In defining entropy values to different molecules, the procedure used involves assigning simple component atoms and molecules arbitrary (often zero value) measures of free energy and enthalpy, at their standard conditions, and using this basis to make thermodynamic tables of entropy and enthalpy values for different reactions, and using reaction algebra to assign entropy values to more complex structures.
Big bang theory In cosmology, the universe prior to the inception of the big bang is often theorized to have been in a low entropy state, about the size of a golf ball, in its initial state some 13.7 billion years ago, as current science understands things. 
Supposedly, it was Belgian mathematical physicist Georges Lemaitre (1894-1966), in circa 1920-1927, after previously studying relativity under Arthur Eddington, who conceived a “firecracker theory”, wherein building on thermodynamics and problems of Albert Einstein’s static universe model, he was led into the view that if the universe is increasing in entropy, according to the second law, that it must be finite: subsequently there would have had to been a time when the entropy of the universe was low.  The details of this, assertion, however, need to be fact checked.
References 1. (a) Penrose, Roger and Gardner, Martin. (1999). The Emperor’s New Mind: Concerning Computers, Minds, and the Laws of Physics (409-12). Oxford University Press. (b) Davies, Paul and Gribbin, John. (2007). The Matter Myth: Dramatic Discoveries that Challenge our Understanding of Physical Reality (pg. 127). Simon and Schuster. 2. Greene, Brian. (2004). The Fabric of the Cosmos: Space, Time, and the Texture of Reality (pgs. 173-74). Random House. 3. Temporal problems solve all physics problems (2010) – PhysicsForums.com. 4. Graves, Dan. (1996). Scientists of Faith: Forty-Eight Scientists and Their Christian Faiths (pg. 160). Kregel Resources.