Originally, the powerhouses of higher cells, the mitochondria, were independent organisms. Researchers at Goethe University Frankfurt have investigated to what extent their metabolism has blended with that of their host cells in the course of evolution, using the example of a mitochondrial stress response. They have discovered that mitochondria send two different biochemical signals. These are processed together in the cell and trigger a support mechanism to restore cellular balance (homeostasis). The work was partly done within the ENABLE cluster initiative (now EMTHERA) at Goethe University Frankfurt.