In bioethics potentiality is almost exclusively discussed in connection with the so called "moral status' of the human embryo. In the few other bioethical contexts, where potentiality plays a role, moral rights of human beings in other circumstances or other entities are at stake, e.g. those of brain dead persons or human-animal chimeras. Human embryo rights have traditionally been discussed against the backdrop of abortion, but meanwhile the discussion extends to embryo and stem cells research as well. There are two standard readings of an embryo's potentiality: according to the first an embryo is "a potential person", according to the second it already is a person, namely one "with potential". These two competing understandings of potentiality lead to different accounts of embryo rights as well as to a discussion about the concept of potentiality itself. In this context two further problems arise, one about what it means to be a person, another about issues of identity between the early embryo and the later child and adult. In addition to that, the concepts of "potentiality", "personhood", and "identity" are closely interwoven, such that each has a strong impact on the other two.