Increasing evidences suggest that the fragments of mitochondrial genome is found in nuclear genome of both normal and cancer cells. The phenomenon of such nuclear integration of mitochondrial genome is named as numtogenesis. Numtogenesis also occurs during aging and may contribute to other human diseases. Although transfer of mitochondrial DNA (mtDNA) inside the nucleus is known for sometimes, the underlying mechanisms remained unclear. Now a paper by McArthur et al. (2018) shed lights on how mtDNA escapes from the mitochondria to outside the cell through BAK/BAX pores in the outer membrane after the loss of cytochrome c during the apoptosis. It is conceivable this escape mechanism also underlies numtogenesis.