Although education experts are increasingly advocating the incorporation of integrated Science, Technology, Engineering, and Mathematics (STEM) curriculum units to address limitations in much current STEM teaching and learning, a review of the literature reveals that more often than not such curriculum units are not mediating the construction of in-depth STEM knowledge. In this paper, we conjecture that the challenge of generating integrated STEM curriculum units that overcome this limitation and facilitate in-depth learning of and about STEM can be met by the use of three types of big ideas: "within-discipline big ideas that have application in other STEM disciplines," "cross-discipline big ideas," and "encompassing big ideas." We provide a six-component framework (together with an example of the framework in action) that can be used to scaffold pre- and in-service teachers' development of integrated STEM curriculum units based around these types of big ideas. The paper concludes by discussing possible directions for future research and development in this field.