During photosynthesis, light energy is used by photosystems I and II to establish electron flow, which ultimately results in the production of ATP and NADPH. Two modes of electron flow exist, a linear electron flow and a cyclic electron flow (CEF). The latter pathway generates more ATP, but its molecular components have been elusive. Here, a combination of biochemical and spectroscopic techniques has been used to identify the supercomplex that drives CEF in the green alga Chlamydomonas reinhardtii