Extending work in the history and anthropology of sciences, Fortun uses developments in asthma research to elaborate practices of “care” among genomic scientists today: their love of data; their worry over its creation, preservation, and analysis; their laborious attention to collective technical infrastructure; and the cultivation of scientific subjects appropriately anxious about genomic truths. He analyzes “care” as an ensemble of differentiated practices or frequencies—curation, scrupulousness, solicitude, and friendship—that, although intimately related, are attuned to different objects, scales, and practices in the sciences. He also gives a partial genealogy of asthma genetics research, and its rapid transformation from a focus on fairly simple, linear genetic explanations in the 1990s, through the more complex genome wide association studies of the 2000s, to today’s “geneXenvironment interaction” research, in which an open- ended asthma genomics is being experimentally melded with the air quality and exposure sciences. These new developments have depended on intensive investment in informatics infrastructure as a critical public resource, while demanding new popular and scientific understandings of the science itself, with significant cultural and political import.