Shortly after Johannes de Sacrobosco published his astronomical treatise De sphaera in the thirteenth century it began a process of transformation and a commentary tradition over more than 350 editions within the next 400 years. This commentary tradition helped in shaping the development of scientific enquiry in Europe by circulating continuously adapted and transformed ideas and knowledge. In due course, it became one of the most influential textbooks of the early modern university. This chapter describes the knowledge tradition in and around the Sphaera, as well as its contents, and the research project The Sphere at the Max Planck Institute for the History of Science. This project investigates a corpus of 359 Sphaera editions and explores the textual and visual features of the editions, while developing hypotheses on the knowledge disseminated through the textual and visual levels of the book. For this, several computational tools were developed within the framework of the project that were used for the investigation of the volvelles contained in the corpus.