Introducing the enzyme H+-ATP synthases (or FoF1-ATP synthases) catalyze the formation of ATP from ADP and inorganic phosphate in the membranes of mitochondria, chloroplasts and bacteria. Endergonic ATP synthesis is coupled to proton translocation across the membrane and is thereby driven by a difference of the electrochemical potential of protons, which is generated by oxidative phosphorylation or photosynthesis. H+-ATP synthase is thought to contain two rotary motors converting electrochemical energy via a mechanical form of energy to chemical energy. We apply a single-molecule spectroscopy approach to monitor the internal rotation of the g-subunit of the F1 part against its static counterpart, the b-subunits of the Fo part. In addition, we investigate the rotation and conformational changes of the  e-subunit of the F1 part, which might regulate the direction of catalysis, i.e. control of ATP synthesis or ATP hydrolysis. A detailed analysis of the Fo motor (c-subunit movement versus the a-subunit, and helix rotation within one c-subunit) is following.