It is a fertility treatment involving the donation of oocytes from an anonymous donor to a couple or a single woman. Requirements: An initial visit to the clinic in Thessaloniki, in order for the patient to be informed about the oocyte. donation program and the Greek legislation, while performing all the necessary tests by the medical team. After the donor selection, patient is required to start treatment a hormone and ultrasound follow up of their endometrium, either on the clinic or in their home country. After the endometrium is ready, patient must come again in the clinic for the embryo transfer, where all available oocytes are fertilized with the male partner’s sperm. Assisting Nature selects the most appropriate donor based on: ovarian reserve age appearance educational and social status.