Infertility is a major problem in the human population. Despite significant advances in assisted reproductive technologies, such as in vitro fertilization (IVF), a pregnancy can only be established in 30% of IVF-cycles, as the quality of the embryo plays a major role in initiating the pregnancy. Recently our group has demonstrated the release of microRNAs and extracellular vesicles (EVs) by bovine embryos into the culture medium. We also isolated EVs from medium conditioned by human embryos. MicroRNAs and EVs are important for communication from one cell to another, influencing the translation of genes to proteins and they play a regulating role during biological processes, including pregnancy. We hypothesized that EVs released by a high quality human embryo, which has the potential to create a pregnancy after transfer, differ from EVs released by low grade embryos which do not initiate a pregnancy. Here, we want to extract EVs from culture medium conditioned by human embryos that were selected for embryo transfer. We will provide evidence for internalization of EVs in an endometrial cell line model in response to EVs of implanting and non-implanting embryos. Finally, we will retrospectively compare the contents of EVs isolated from embryos that initiated a pregnancy, with those of embryos that did not induce a pregnancy. As such, we may be able to identify biomarkers for good quality embryos before transfer.