This paper introduces a fresh perspective on product modularization and proposes a process for modular product realization called Holonic Product Design (HPD). The holon has recently been adopted from Arthur Koestler's work to represent subsystem entities within manufacturing systems and the enterprise chain. In addition, it has been embraced as a philosophy for change that attempts to fashion modern manufacturing businesses and manufacturing activity. This paper demonstrates the holon as being equally valid as an approach to product development. Through research at a number of UK companies, HPD is developed and presented as a structured approach to product realisation. Addressing a total view through systems engineering, HPD provides an accessible and customizable modular product development workbook. The efficacy of the new approach is demonstrated through the initial results from an HPD case study. Further work remains in refining the integration of HPD elements and thoroughly testing the approach through a full new product development process.