For decades, scientists have believed that women were born with all the eggs they would ever have and that no new ones could ever be made. Recently a group of researchers in the USA isolated a primitive "stem" like cell from the ovaries of adult women. These cells were shown to be capable of forming what appeared to be new eggs (oocytes) when they were injected back into ovarian tissue. The implications of this are potentially enormous, but at the moment we know very little about what these cells may or may not be capable of. If we could make new eggs we could eventually help restore fertility in women who have become infertile for a variety of reasons, including chemotherapy, early menopause or just normal ageing. However, these findings have led to controversy and many questions remain as to whether these new eggs can develop normally. This project will determine whether these cells can be isolated from the ovaries of healthy women from a range of ages. Then using a system which we have developed where we can grow eggs outside the body (culture system), we will determine whether these cells can form new eggs and whether they are normal. The ultimate end point of this work would be to determine whether these cells were capable of forming eggs that could be fertilised and form embryos.