The article introduces the reader to preparative chromatography as a purification tool for the manufacturing of active pharmaceutical ingredients (APIs). In a first part, the history of the development of chromatography as a separation technique is reviewed and concepts associated with the process development and its modeling are introduced. In a second section, the various techniques used to optimize a preparative separation for production are reviewed. Aspects of the various phases of the process development from early clinical phase up to commercial manufacturing are discussed with emphasis on intellectual property, solvent considerations, and separation robustness. Scale-up rules are also introduced at the end of the section. Finally, the author discusses the implementation of a chromatographic step at commercial scale; handling of the chromatographic packing material and plant operations are more specifically highlighted.