The multidisciplinary systems biology approach that is needed to assess endometrial receptivity should be used to understand the reciprocal dialogue between the embryo and the decidualised endometrium. This chapter focuses on human embryo research and the development of appropriate functional models of implantation that will allow the investigation of molecules mediating blastocyst-endometrial/decidual interaction. Ectopic pregnancy could be considered as a model to study the failure or the absence of mechanisms that limit implantation. Experience with cell nuclear replacement has identified the key role of cytoplasmic and nuclear factors for normal embryonic development. The conventional measurements of sperm concentration, motility and morphology only act as surrogate markers of fertility. Pre-implantation genetic diagnosis (PGD) should be carried out by specialist centres that have a multidisciplinary genetic support infrastructure including genetic counselling, and clinical pathology accreditation (CPA) qualified cytogenetics and molecular genetics laboratories.