This article explores long-standing symbiotic relationships between women and microbes in Iceland while analyzing the transformation of this relationship in the making of the dairy product skyr during the twentieth and twenty-first centuries. In the past, differences in microbial cultures and production methods meant that the taste and texture of milk varied greatly. Standardization and technological innovations have steadily impoverished its microbial diversity over the past 120 years. Starting from a historical account of skyr making, we zoom in on skyr in the twenty-first century, a period in which skyr has had an international breakthrough, captured in branding efforts and advertising campaigns produced in this decade for various types of skyr from producers in Iceland, Europe and the United States.