Mitochondria are a membrane-enclosed organelles found in most eukaryotic cells. Mitochondria are sometimes described as “energy house” because they generate adenosine triphosphate (ATP), which is used as a source of chemical energy. In addition, they are involved in cell signaling, cellular differentiation, cell growth, cell cycle and cell death. However, the exact role of mitochondria during in vitro embryo production technology wasn't fully understood; especially the repositioning of active mitochondria during oocyte maturation, fertilization, and culturing. So, this study aimed to clarify the relationship between oocyte maturation and the repositioning of active mitochondria. It has been found and in contrast to previous reports that repositioning of active mitochondria isn't an utter sign to completion of oocyte maturation. In addition, oocyte mitochondria have fine crystal shape, other than, coarse particles in previous reports.