The word “organoids” means “organ-like” entities. They are small biological constructs, grown in vitro from stem cells, to mimic structures, functions and diseases in the real body. As emerging technologies, they are associated with tantalising visions of future potential applications. The focus of this book is to assess one such vision: The idea of using organoids derived from patients to guide precision medicine in clinical cancer care (oncology). The book firstly offers a description of this vision and then a careful evaluation of its plausibility and uncertainties. The assessment of visions and emerging technologies is a vexing methodological problem at the intersection of philosophy, ethics, and health technology assessment. It is challenged at once by the very real impact visions have on human action in the present and the lack of evidence for something that has not yet come to pass. This work therefore also provides methodological innovations for evaluating visions and emerging technologies in healthcare, a field that provides fertile ground for philosophical work.