A human ovary grown in the lab using slivers of ovarian tissue can turn an immature egg into one that is ready to be fertilized. This can have mnay health benefits such as that women who have previously been unable to fertlise their eggs a higher chance of conceiving. It creates an artifical environment outside the body and by the use of a sex hormone oestradiol the egg is able to mature in around 72 hours. At this point the egg developed a polar body and can be used. This also means that women can take previously immature eggs and freeze them when before they had to be mature.