The paper reports the crystal structure of photosystem II (PSII) from *Thermosynechococcus vulcanus* at 3.7 Å resolution, providing detailed insights into the molecular interactions and cofactor arrangements within the complex. The structure is built using sequences of large subunits D1, D2, CP47, and CP43, as well as extrinsic proteins and low molecular mass subunits. Key findings include the arrangement of chlorophylls and cofactors, including two β-carotenes near the reaction center, which offer clues to secondary electron transfer pathways. The structure also reveals that the C-terminal part of D1 polypeptide directly ligates the Mn cluster, and possible ligands for the Mn cluster are identified. These findings enhance understanding of PSII's mechanism of action, particularly in water-splitting and electron transfer processes.The paper reports the crystal structure of photosystem II (PSII) from *Thermosynechococcus vulcanus* at 3.7 Å resolution, providing detailed insights into the molecular interactions and cofactor arrangements within the complex. The structure is built using sequences of large subunits D1, D2, CP47, and CP43, as well as extrinsic proteins and low molecular mass subunits. Key findings include the arrangement of chlorophylls and cofactors, including two β-carotenes near the reaction center, which offer clues to secondary electron transfer pathways. The structure also reveals that the C-terminal part of D1 polypeptide directly ligates the Mn cluster, and possible ligands for the Mn cluster are identified. These findings enhance understanding of PSII's mechanism of action, particularly in water-splitting and electron transfer processes.