Technologies enabling 'mitochondrial transplantation' have the potential to mitigate future suffering; to prevent the inheritance of mitochondrial diseases. When considering the use of germ-line modification of the type I will consider there are some who claim such modifications do not avoid the 'impersonal harm/benefits' arguments; that depending on the timing of our actions genetic modification may affect numerical-identity, or perhaps even personal-identity (narrative-identity). The aim of this book is to contextualise the process of mitochondria germ-line modification within a detailed examination of our identity. I consider the potential of affecting identity in the context of both naturally occurring reproductive events and in respect of known identity-affecting events, in order to make the claim that the types of affects to either numerical-identity or personal-identity, resulting from mitochondria germ-line modification, should not in any sense be considered morally problematic.