Cyanobacteria share general prokaryotic properties and include unicellular, colonial and filamentous forms. Cyanobacteria are commonly called as blue green algae due to presence of blue green pigment c-phycocyanin, C-phycoerythrin along with chlorophyll ‘a’, β-carotene and some myxoxanthin. Fossil of blue green algae make up layered formations which are called as stromatolites. These are probably the 1stO2 producing organisms to evolve. These are responsible for early accumulation of atmospheric O2. It is related to bacteria, their photosynthetic apparatus includes both chlorophyll ',a'carotenoids and phycobiliprotein pigments.