As we apply the principles embodied by quality by design to gain a deeper understanding of our chemical manufacturing processes for active pharmaceutical ingredients (API), we are challenged with effectively describing the design space in terms of chemical and engineering principles (i.e. via a science based approach). One approach is to combine the appropriate scientific principles, process modeling tools, and multivariant designs to capture and describe the process outputs . In addition we are challenged with understanding and addressing the subtle but important scale up effects, the limitations of equipment to produce optimum process conditions for reactions and isolations, and process control. Developing and leveraging the expertise to perform these activities has potentially immense benefits in process understanding and process design. In this presentation, we present examples that illustrate how chemical engineering is critical toward fully realizing the benefits of quality by design