The talk will investigate how scientists' understanding of the question "what is the world made of?" was transformed in the second half of the twentieth century, even in the absence of major conceptual shifts (such as the quantum and relativity revolutions of the early twentieth century had been). The talk will draw on numerous examples from the work of the research group "Historical Epistemology of the Final Theory Program" (most notably Werner Heisenberg's 1958 Weltformel) to illustrate the complex interaction of "content and context" in scientists' engagement with such "eternal questions". The entire investigation is thus placed in the context of a wider research program of a history of eternal questions.