Upon exposing etiolated leaves of dark-grown plants to light, chlorophyll synthesis begins, concurrently accompanied with the reorganization of prolamellar body in etioplasts. During the light-dependent greening of etiolated leaves, the lamellar structure in chloroplasts is developed and the photochemical activities of chloroplasts are also differentiated. Namely, development of photosynthetic apparatus is controlled by light. These phenomena are highly attractive for biologists, and have been investigated by many workers including us. The purpose of this review is to outline the following problems: (1) the phototransformation of protochlorophyllide to chlorophyllide in etiolated leaves and in extracted protochlorophyllide holochrome, (2) the development of prolamellar body in etioplasts, (3) the differentiation of cyclic and non-cyclic photophosphorylations in the greening course of etiolated leaves.