The chemical ATP, adenosine triphosphate, is the fuel that powers all life. ATP is found in all known forms of life, where it provides energy to drive muscle contraction, impulse propagation and chemical synthesis. Despite ATP’s central role, the structure of the enzyme generating ATP, F1Fo-ATP synthase, in mammals, including humans, has not been known so far. Now, Leonid Sazanov and his group at the Institute of Science and Technology Austria (IST Austria) report the first complete structure of the mammalian F1Fo-ATP synthase. This structure also settles a debate on how the permeability transition pore, a structure involved in cell death, cancer, and heart attacks, forms.