Where there is oxidation there will always be reduction. Oxidation was coined by Morveau and Lavoisier in 1790 from the French ox(ygène) and (ac)die and reduction was coined around the same time from “re” meaning “back” and “ducere” meaning to “bring back” in the sense of lower, diminish or lessen (Online Etymology Dictionary, http://www.etymonline.com). In this sense an oxidizing agent gives oxygen to another substance or removes hydrogen (loss of electron) from it while a reducing agent carries out the opposite reaction. Industry is increasingly exploiting this duality for the production of industrially relevant intermediates for active pharmaceutical ingredients (APIs). In some cases the oxidized product is of interest and sometimes the reduced product. These enzymatic reactions are carried out under mild conditions with often high regio- or enantioselectivity compared to their chemical counterparts and in the case of enzymatic oxidation over-oxidation can be avoided in most cases. The key to the successful use of an enzymatic oxidation or reduction reaction in large scale is the regeneration of the redox partner in order to reach economic targets for the process.