In our recent research, we have used respiration-deficient tumour cells to challenge the dogma that mitochondria with their genome are constrained within cells in the body, and to question the concept that mitochondria are primarily the powerhouse of the cell. Our results have shown that mitochondria move from normal cells in the body to tumour cells without mitochondrial DNA (mtDNA), resulting in respiration recovery and the ability to grow as tumours [1, 2]. Almost a decade earlier, a similar phenomenon had been show in co-cultures of human tumour cells lacking mtDNA with mesenchymal stem cells [3]. The strength of both of these ground-breaking studies was that they used mtDNA polymorphisms to show repopulation of tumour cells with mtDNA, establishing the origin of mitochondria in the donor cells.