Respiration is the “ying” to photosynthesis’ “yang”. Broadly defined, respiration is the transport of electrons coupled to the pumping of protons. Anaerobic respiration is fundamental to many biogeochemical cycles, and aerobic respiration was likely key to the evolution of complex multicellular life. But where did respiration come from? How did life “learn” to breathe? In this talk, I will: (i) present an evolutionary history of the respiratory electron transport chain; (ii) explain how the biochemistry of primitive electron transport complexes is broadly consistent with what is known about the availability of electron acceptors and metal cofactors through deep time; (iii) highlight how modern microbes with ancient forms of respiratory complexes may give glimpses of life’s first breaths.