The cyanobacteria are permanently dominated in freshwater systems and sometimes in marine ecosystems. Most of them can produce dense mats called harmful algal blooms (HAB) on water surfaces and break the ecosystem balance. Some cyanobacteria can produce highly potent toxins known as cyanotoxins. The release of these toxins into the surrounding water occurs mainly during cell death and lysis or as opposed to continuous excretion from the cyanobacterial cells. Some cyanobacteria species can release toxins (extracellular) into the water without cell rupture or death. These cyanotoxins are produced by a wide variety of planktonic unicellular or multicellular cyanobacteria. Some of the most commonly occurring genera are Microcystis, Dolichospermum, and Planktothrix, responsible for producing cyanotoxins like Microcystins, Anatoxins, Cylindrospermopsin and Saxitoxin. This project aims to understand the biological and morphological patterns underlying the cyanotoxin production of filamentous and unicellular cyanobacteria. The study will expand the understanding of cyanotoxin releasing mechanisms of cyanobacteria.