Cyanobacteria are among the earliest of inhabitants of Planet Earth and are highly diverse members of the current global biodiversity and are making significant contributions to the Carbon and Nitrogen bio-geochemical cycles, particularly in the deep oceans. Cyanobacteria in recent year have gained importance because of their potential use in various areas of research. This diverse group has application in various fields like biotechnology, pharmacology, agriculture etc. Due to presence of wide spectrum of bioactive compounds cyanobacteria has possesses antiviral, antibacterial, antifungal and anticancer activities. Several strains of cyanobacteria are also rich in food supplements. Further nitrogen fixing capacity of cyanobacteria has attracted agriculturists and researchers and they used blue green algae as a component of biofertilizers to improve both the fertility of soil as well as growth of plants. Recent studies have also shown that cyanobacteria have capability to degrade environmental pollutants and are also being used as a promising source of alternative energy. In spite of all these investigation and research more efforts should be made in search of more strains of cyanobacteria and genetically modifying known strains to ensure maximum production of the desired products.