It is well documented that the KRAS oncogene efficiently transforms non-malignant cells, and there is some evidence for the role of mitochondria in this process. Now Peng Huang and colleagues show that K-Ras induction results early on in mitochondria assuming the phenotype consistent with the so-called Warburg effect, i.e., increased glycolysis and attenuated oxidative phosphorylation. Thus the K-Ras protein capable of swift induction of phenotypic changes typical of cancer cells, yet these changes are reversible, and for cells to irreversibly reach their full malignant potential a much longer K-Ras expression is required, implicating mitochondria in the longer-term effects of the oncogene.