Female mammals – including humans – are born with all of their egg cells. Of a woman’s one to two million egg cells, about 400 mature before menopause and can be fertilized. Some egg cells therefore survive for several decades – and need to remain functional over this long time. Extremely long-lived proteins in the ovary seem to play an important role in this, as teams of researchers from Göttingen (Germany) have now discovered in experiments with mice. These long-lived proteins appear to help maintain fertility for as long as possible.