Abstract: The fundamental principles underlying ultrafast energy and electron transfer in primary photosynthesis is reviewed from a physical point of view. The basic theories such as Fermi's golden rule, F?rster and Dexter energy transfer, Marcus electron transfer theory, and exciton theory are introduced. Their common features, conditions for applicability as well as discrepancies are discussed. The aim is to interpret the relation between protein structure and its functions in terms of physical principles, and thus to delineate the main threads of this research field.