The embryo sac is the mature female gametophyte of the angiosperm which is a 7 celled 8 nuclei structure. In it, at the chalazal end there are cells called antipodal cells which act as nutritional centre. Female gamete is surrounded by two synergid cells which help in the fertilization process and present at the micropylar end of the sac. In the centre of the sac, polar nuclei is found which is a cell with two nuclei. The ploidy level of synergids, antipodal cells and female gamete 'n' but the polar nuclei is '2n'. It is similar to the nucellus (2n) tissue cells which have not participated in the megasporogenesis process.