Photochemical hydrogen production is potentially one of the most fascinating ways for solar energy conversion and storage. Since 1977, several homogeneous, quasi-homogeneous or microheterogeneous model systems of hydrogen or oxygen generation from water, by visible-light irradiation, have been proposed and are briefly reviewed. These half photosystems are based on different approaches: (i) multimolecular systems, (ii) systems involving a supramolecular structure of polyad type, and (iii) systems incorporated in organized and constrained or confined media. A survey of the different attempts for complete water splitting into hydrogen and oxygen is also made.