Although epigenetics represents an emerging field of biological research with a potentially large influence on society as well as conceptual implications on how genetics is understood, it is often not a part of the biology education provided at secondary schools. Therefore, this educational research design study describes the development of a teaching design about epigenetics, created in collaboration with researchers and practicing teachers, and included the aim of updating genetics education to appropriately mirror contemporary biology research frontiers. The study was conducted in 11 upper secondary school classes. The resulting teaching design consists of a set of "Big Ideas" and teaching and learning activities that can be used with different groups of students and integrated into regular genetics education. Despite the complex content, the students appreciated the topic and found it not only to be highly relevant, but also understandable. The teaching design, which centered on human biology and the interplay between genetics and the environment, resulted in participants articulating a nuanced understanding of these two topics, which indicates a potential shift in perspective away from genetic determinism. The design also provided better explanatory models for various biological phenomena that had already been included in the curriculum, such as cell differentiation. Teaching epigenetics based on contemporary research was reported to be inspiring by the teachers, and students felt that it was exciting to learn about concepts at the frontline of scientific research. Thus, epigenetics is also relevant as a context for teaching the nature of science. A challenge identified in the study was how to avoid conflicts between old and modern explanatory models in genetics, an issue that needs to be explored further.