1. Oocytes increase in number through mitosis and evolve into primary oocytes, which are surrounded by follicular cells to form follicles. Female animals complete the first meiosis before and after ovulation, producing secondary oocytes and the first polar body, which enter the fallopian tube and are ready for fertilization with sperm.

2. Remove the nucleus of secondary oocytes by micromanipulation. Because the nucleus of the secondary oocyte undergoing meiosis is located near the first polar body, the nucleus can be sucked out together with the first polar body with a micropipette.