Cancer stem cells are the new targets of the 'war on cancer' launched by Richard Nixon in the 1970s. When the role and existence of the so-called cancer stem cells was revealed to the public as a potential therapeutic strategy against cancers, it quickly gained attention from researchers and the public. This chapter describes how cancer stem cells came into existence and briefly outlines the general theory that supports the promise of targeted cures of cancer. It questions the ontological assumption underlying the prospect of such targeted cures. The chapter argues that the ontological status of stem cells is a crucial issue that deserves research attention. Cancer stem cells (CSCs) are cancerous cells with 'stemness' properties. The emergence of the cancer stem cells hypothesis is not alien to the growing public fear of nuclear power. If stemness is a disposition, then the CSCs can be distinguished from non-CSCs and specifically targeted in order to cure cancer.