each step of a synthesis involves a chemical reaction, and reagents and conditions for each of these reactions need to be designed to give a good yield and a pure product, with as little work as possible. a method may already exist in the literature for making one of the early synthetic intermediates, and this method will usually be used rather than "trying to reinvent the wheel". however most intermediates are compounds that have never been made before. these will normally be made using general methods developed by methodology researchers. to be useful, these methods need to give high yields. they must also be reliable for a broad range of substrates. for practical applications, additional requirements include industrial standards of safety and purity. methodology research usually involves three main stages: "discovery", "optimization", and studies of "scope and limitations". the "discovery" requires extensive knowledge of and experience with chemical reactivities of appropriate reagents. "optimization" is where one or two starting compounds are tested in the reaction under a wide variety of conditions of temperature, solvent, reaction time, etc. researchers try different conditions until they find the best conditions for product yield and purity. finally, researchers try to extend the synthesis method to a broad range of different starting materials, to find its scope and limitations. total synthesis (see above) are sometimes used to highlight the new method and demonstrate its value in a real-world application. major industries focused especially on polymers (and plastics) and on pharmaceuticals have used this research.