There are mechanisms that keep the germ line immortal, for instance, in the differentiation of oocytes, the oocyte cytoplasm is purified through enriching only faultless organelles while damaged ones are offloaded into cells destined to die, and the genomes undergo epigenetic reprogramming in preparation for the next life cycle. Once the mechanisms in the cycle are understood, we will be able to manipulate cells to do similar things, such as purifying cytoplasm or overwriting their totipotent states by epigenetic reprogramming, which can be used in the treatment of age-related diseases.