In the context of this book, innovation is about achieving desirable goals in domain-specific education. The various contributions to the second part of the book provide knowledge about how to achieve something worthwhile in a particular domain, and all do so in the form of design principles as a result from design research. Such principles are popular in design research and other approaches to innovate educational practice, but education and educational research would benefit from further reflection on what they are and how they are grounded in research and practice. My commentary therefore reflects on design principles in design research. For the various chapters, I analyze whether the design principles as formulated are values, criteria, predictions, advice, or heuristics. I argue that design research would benefit from more clarity of the nature of design principles, and what counts as empirical support. Moreover, I reflect on how design principles could be communicated in a succinct form so that they can inspire others to use them wisely in educational practice.