...This paper presents a unique method of controlling the quality and quantity of mitochondria transferred to single cells using an automated optical tweezer-based micromanipulation system. The proposed method can automatically, accurately, and efficiently collect and transport healthy mitochondria to cells, and the recipient cells then take up the mitochondria through endocytosis. The results of the study reveal the possibility of using mitochondria from fetal mesenchymal stem cells (fMSCs) as a potential source to reverse the aging-related phenotype and improve metabolic activities in adult mesenchymal stem cells (aMSCs). The results of the quantitative polymerase chain reaction analysis show that the transfer of isolated mitochondria from fMSCs to a single aMSC can significantly increase the antiaging and metabolic gene expression in the aMSC. The proposed mitochondrial transfer method can greatly promote precision medicine for cell therapy of mtDNA-related diseases.