Various stages of follicle development in Aceh cattle ovaries after vitrification with BPE: A: primordial follicle; B: primary follicle; C: secondary follicle with oocyte; D: damaged secondary follicle with oocyte; E: tertiary follicle; F: de Graaf follicle (o: oocyte; g: granulosa cell; zp: pellucida zone; af: antrum folliculi). Scale bar=200 µm. Magnification 10x.