By growing Chlorella protothecoides in a medium rich in glucose and poor in nitrogen source (urea), entirely chlorophyll-less cells, called “glucose-bleached’ cells, were obtained. These cells were found to have neither discernible plastid structures nor photosynthetic activities. When these cells were incubated in a nitrogenenriched mineral medium without added glucose, a remarkable formation of fully organized chloroplasts occurred in the light and only partially organized chloroplasts were developed in darkness. In the dark-incubated algal cells a small but appreciable amount of chlorophyll was formed, being accompanied by development of significant activities for the PMS- and FMN-catalyzed photophosphorylations and the HILL reaction. The development of the capacity for performing photosynthetic CO2-fixation, however, was negligible. During the process of “re-generation” of chloroplasts in the light, there occurred active formation of chlorophyll followed by development of all the photic activities mentioned above. Chlorophyll formation as well as development of the photic activities proceeded first in a manner of autocatalytic reaction and later in the form of the first-order reaction. It was inferred that the light-absorbing agent which mediates the chlorophyll synthesis is chlorophyll itself. The activities for the PMS- and FMN-photophosphorylations, the HILL reaction and photosynthetic CO2-fixation were recognized already in the algal cells at an early stage of greening in the light, in which the “discs” were developed but no complete lamellar structure was observed. Further processes of increase of these photosynthetic and related activities—as measured at a high and a lower light intensities—were studied in relation to the chlorophyll formation under continuous illumination and under light-dark conditions. It was found that the PMS-photophosphorylation activity was developed always in parallel with the chlorophyll formation under these different light conditions. Development of the activities for the other photic reactions, however, lagged, to different extents, behind the formation of chlorophyll in the later phase of greening of algal cells under these conditions. Based on these results the modes of formation of the components involved in these photic reactions were surmised.