The Fine Chemicals industry is concerned with the manufacture of relatively small volume products by multistage manufacturing processes. Pharmaceuticals, agrochemicals, colouring materials and biocidal compounds are typical examples. Understanding the fundamental science behind these chemical processes is of great benefit in the development of efficient, high-yielding and environmentally friendly processes. However, there are no other texts which specifically address this topic by covering the physiochemical principles underpinning the subject. This primer outlines the strategy for obtaining the requisite data, and then goes on to outline the chemical and chemical engineering concepts involved in process development. These include a description of pre-reaction equilibria in single and two-phase systems, factors influencing selectivity in competing reactions, mixing effects in single and two-phase reactions, the science behind workup processes, and a discussion of the principles behind scale-up.