Chloroplasts of higher plants contain thylakoid membranes differentiated into several cylindri- cal granum stacks of appressed (stacked) membrane which are surrounded by non-appressed (unstacked) helically organized stroma thylakoids. The light reactions of photosynthesis are mediated by chlorophyll- protein complexes – Photosystem I (PSI) and Photosystem II (PSII) differentially embedded in granum and stroma membranes. Moreover, electron transport and conversion of light energy into ATP depend on cytochromes b6f and ATP synthase complexes. The photosystem core complexes are organized into large protein-pigment complexes with specific peripheral antennae, chlorophyll-binding light-harvesting com- plexes, LHCI and LHCII. Trimeric, mobile LHCII antenna and LHCII-PSII supercomplexes build up microdomain structure or megacomplexes, which determine the thylakoid structure. Furthemore, the flexible mechanisms of photosynthesis in response to environmental factors are closely related to rearran- gement of supercomplexes in thylakoid membranes.