Suppose that John and Mary Powers arrange to have their fertilized egg, or preembryo, frozen for future use. Suppose John is killed in an airplane crash. Should Mary have the legal right to bring the preembryo to birth? To hire a surrogate mother for that purpose? To have genetic surgery performed upon it to change its future behavioral characteristics? To donate it to gene research? To donate it to another couple? What should be the rights of the genetic donors to custody of a preembryo?