Many Germans, particularly in the eastern part of the country, associate rapeseed with the color yellow. Yellow rapeseed flowers are omnipresent in late April and May, and driving through the country at that time of the year means driving through yellow. It is thus understandable that Sarah Waltenberger begins her monograph picturing a tour through the German countryside on a random Sunday in spring. The book stems from her dissertation at the University of Bielefeld in 2018, and she clearly shows that the yellow flowers indicate more than spring: they are a testimony to the significant role this crop has played in German agriculture.Rapeseed is cultivated for its oil, which finds use in food production and industry, and the residue of the milling process serves as fodder. According to the title, Waltenberger aims at writing the history of rapeseed as Stoffgeschichte, and in her introduction she often uses the word Stoff. The term means “material,” “substance,” and “thing,” among others, and is part of the word Rohstoff, meaning “resource.” The term kindles associations with scholarship in the fields of materiality/material cultures and the history of things. Waltenberger cites many works stemming from this scholarship; however, she falls short in explaining which field her work connects with and why she prefers the term Stoff over Material or Ding.Waltenberger positions her study within Niklas Luhmann's social systems theory, analyzing the perception of rapeseed among various groups involved in its creation. She defines these actor groups as producers, breeders, politicians, and consumers, each with their own perceptions of rapeseed. From these considerations, she develops four central arguments for her study. The first is that rapeseed has been created. It was a crop constructed culturally, but also physically through breeding. This argument plays out very well throughout the book and is probably the most important insight.Her second argument is that rapeseed encoded an understanding of nature, though this point is not effectively illustrated and analyzed. Waltenberger's third argument is that rapeseed had its own agency and was not a passive object. The point clearly connects to her reflections on Stoff, and it would thus have been even more relevant if the book were more clearly positioned in the field of material cultures. The fourth argument relates to the actor groups, who built what she calls the world of rapeseed, protected by communication and trust across the groups (22). It is less clear what the danger to this world was.The introduction is followed by a short chapter on harvest numbers and areas planted from 1880 onward, the botanical features of the crop, and the historical development and characteristics of some rapeseed varieties. The information is useful for understanding the main part of this monograph, in which Waltenberger analyzes the causes of increasing rapeseed production in Germany. Here she works with mainly governmental sources but includes publications from contemporary actors as well.Rapeseed became an oil crop of significance especially in World War I and during the Nazi era, when Germans suffered from fat shortages, leading slowly to the idea among politicians that rapeseed could solve the problem. Rapeseed oil was edible but didn't taste good, and using the residue from the milling process was possible but only to a limited extent. A central insight is that rapeseed's status as a promising crop depended on governmental agricultural support.One of the strengths, but certainly also challenges, of the book lies in the fact that Waltenberger chose to include both postwar German states. Since both states' economies and agricultural systems developed differently, their approaches to and needs for rapeseed differed as well. In East Germany, rapeseed production was relevant immediately after the war. That was because East Germany's ability to import fat was limited and the country relied on domestic resources. In West Germany, production dropped after the war and grew only from the mid-1950s onward. It was spurred by governmental support, so much so that farmers soon faced an oversupply problem, especially internationally. In the 1960s, Canadian breeders developed canola, a variety that gave a less bitter oil and was thus preferred in global markets. West German rapeseed production rose nevertheless, and Waltenberger analyzes the various reasons and challenges behind this development. It was not before the mid-1970s that German breeders also created varieties more suitable for human and animal consumption, and these developments spurred the crop's cultivation even further.That rapeseed is a crop created by people, not a plant given to them by nature, remains the central insight of Waltenberger's study. Some reflections on whether this was true for other, if not all, similar crops might have enriched the point. It would have also enhanced her study if she had carved out more clearly how actor groups overlapped. Too often, Waltenberger remains unspecific, for example when speaking of “politics” or “research” as actors. Many pages do not address rapeseed but problematize fat, especially in the subchapter regarding World War I and the Nazi period, but these rely on the existing literature. Nevertheless, the book is an interesting read that enriches German agricultural history in the twentieth century.