  One issue arises from the fact that some research on stem cell-derived gametes requires the creation of embryos, regardless of whether one is using ESCs or iPSCs.  To establish that a particular technique for deriving human gametes from stem cells produces functional sperm and eggs, it is necessary to demonstrate that the cells can produce an embryo.  This entails the creation of embryos through in vitro fertilization.  Since it would not be safe to implant embryos created during the early stages of the research, the likely disposition of the embryos is that they would be destroyed.  In such instances, the research would implicate all of the moral issues surrounding the creation and destruction of embryos for research.  However, the creation of embryos for research in this situation would not necessitate the destruction of the embryos, as it does when embryos are created to derive stem cell lines.  One could in principle store them indefinitely rather than destroy them.  This would still leave  one subject to the objection that life is being created for instrumental purposes.  But the force of the objection is questionable since it is not clear that this instrumental use is any more objectionable than the routine and widely accepted practice of creating excess IVF embryos in the reproductive context to increase the probability of generating a sufficient number of viable ones to produce a pregnancy. 