Adenosine triphosphate (ATP) is the fuel of life; every living cell needs ATP to carry out its functions. The human body actually synthesizes its own weight in ATP every day. This is achieved by ATP synthase, a protein complex of two joined rotating molecular motors. A detailed understanding of how this system functions will impact our fundamental understanding of life, but also the treatment of neurodegenerative diseases or the development of biomimetic nanodevices. Presently, biomedical science still lacks a sufficient understanding of how ATP synthase efficiently stores energy in ATP. A recent report suggests a new chemical mechanism for this energy storage reaction, the discovery being based on quantum-chemical calculations conducted in the presence of the reaction environment in ATP synthase. The suggestion could constitute an important step towards an understanding of one of the most ubiquitous reactions in all living cells, the synthesis of ATP and its use as cellular fuel.