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The chlorophyll-carotenoid binding proteins responsible for absorption and conversion of light energy in oxygen-evolving photosynthetic organisms belong to two extended families: the Chl a binding core complexes common to cyanobacteria and all chloroplasts, and the nuclear-encoded light-harvesting antenna complexes of eukaryotic photosynthesizers (Chl a/b, Chl a/c, and Chl a proteins). There is a general consensus on polypeptide and pigment composition for higher plant pigment proteins. These are reviewed and compared with pigment proteins of chlorophyte, rhodophyte, and chromophyte algae. Major advances have been the determination of the structures of LHCII (major Chl a/b complex of higher plants), cyanobacterial Photosystem I, and the peridinen-Chl a protein of dinoflagellates to atomic resolution. Better isolation methods, improved transformation procedures, and the availability of molecular structure models are starting to provide insights into the pathways of energy transfer and the macromolecular organization of thylakoid membranes.