The methods of gamete manipulation used in assisted reproductive technology (ART) are rapidly proliferating and in some instances outpacing the underlying science. In this review, we discuss two major advances in the ART laboratory-intracytoplasmic sperm injection and extended embryo culture before embryo transfer. We outline the rationale for these approaches, discuss results of experiments obtained from animal model systems and human preimplantation embryos that provide the scientific basis for these procedures, and point out potential concerns that have arisen from these studies.