It is possible to freeze fragments of the surface of the ovary (known as ovarian cortex); this aspect of the ovary contains large numbers of ovarian follicles at the very immature (or primordial) stage (See my section on The Menstrual Cycle and Ovulation Tracking for more information on follicles). This approach is usually considered in females who are unsuitable for undergoing IVF to freeze eggs, for instance, young girls. However, this technique requires laparoscopic surgery to cut away pieces of ovarian tissue for freezing, which damages the ovary. At present, there are no effective means for developing the very immature follicles found in ovarian tissue outside of the body in the lab. This means that in order to use these immature eggs requires that the tissue be transplanted back in to the body. Obtaining eggs for pregnancy from these transplants then often requires an IVF procedure. There are very few centres in the world with extensive experience in utilising this technique.