[en] Formation of the photosynthetic apparatus in dark-grown 2-day-old bean (Phaseolus vulgaris L.) leaves was studied. The photosystem 2 (PS 2) reaction centres started functioning 1 h after the beginning of irradiation. Electron transport between the two photosystems started after 4 h of irradiation. The PS 2 units were able to transfer the excitation energy to each other after 10 h of greening. The photosynthetic activity appeared a long time before the typical 77 K fluorescence bands of green leaves appeared.