The difference between calling a molecule artificial or natural is a legal definition, not a chemical or biological one. If a molecule of vanillin is isolated in a lab by extraction of a particular seed pod, the chemical is called “natural vanilla.” If that same molecule is made from lignin, which is a polymer found in naturally in wood, that substance is called “artificial vanilla.” The difference is that transforming lignin to vanillin requires chemical steps not covered by the legal definition of the word “natural.” To be clear, the “natural” and “artificial” versions of a molecule are exactly the same chemical species (same atoms, same bonds, same stereochemistry, etc.), but there may be other chemicals present that may differ in the natural and artificial versions of a product.