In oogenesis the oogonium differentiates into oocyte I (2n) and this cell enters meiosis. After finishing the first meiotic division (meiosis I) the oocyte I forms two cells: the oocyte II (n) and the first polar body. The oocyte II is bigger because it gets almost all the cytoplasm and the cytoplasmic structures of the oocyte I as a strategy for metabolite and nutrient storage. The oocyte II cell goes then to the second meiotic division. The first polar body is very small and almost lacks cytoplasm; it disintegrates or stays attached to the oocyte II.