One of the most critical processes determining cyanobacterial eco-physiology is cellular death. Evidence supports the existence of controlled cellular demise in cyanobacteria, and various forms of cell death have been described as a response to biotic and abiotic stresses. However, cell death research in cyanobacteria is a relatively young field and understanding of the underlying mechanisms and molecular machinery underpinning this fundamental process remains largely elusive. However, reports on cell death of marine and freshwater cyanobacteria indicate this process has major implications for the ecology of microbial communities/ Different forms of cell demise have been observed in cyanobacteria under several stressful conditions, and cell death has been suggested to play a key role in developmental processes, such as akinete and heterocyst differentiation, as well as strategy for population survival.