Both sperm and oocytes can be frozen and stored for prolonged periods (even many years). Once thawed, these gametes are used for ART procedures aimed at conception and pregnancy.
These procedures can be used if treatments (for example oncology) that are potentially harmful to the reproductive function need to be carried out and, if you want to delay conception (social freezing). In this way it is also possible to avoid the natural degradation of the quality of the gametes linked to advancing age.