This review examines the properties and uses of carotenoid radicals. Their mechanisms of action on the molecular level play a crucial role in electron transfer and light regulation processes in photosynthesis, in the design of improved artificial solar cells, and in the scavenging of toxic free radicals. There is a remarkable increase in the quantum yield and the lifetime of the charge-separated states of the carotenoid radical cations in the supramolecular "hosts" beta-glycyrrhizic acid (GA) and arabinogalactan (AG).