Ever changing environment affecting the world agricultural productivity and according to an estimate the global　population will reach 9.7 billion by 2050 (DESA, 2015). Therefore, the current situation needs to develop climate smart technologies to improve crop productivity to sustain the ever-rising global population. Current day farmers are introducing a considerable amount of agrochemicals to enhance crop productivity. Indiscriminate agrochemical application has altered not only the soil physic-chemical and biological properties but has also affected human health through food chain contamination.

Agriculturally essential cyanobacteria under these changing environmental conditions may resolve the problem significantly without changing the natural soil properties. Unfortunately, most of the cyanobacterial stress management and signalling pathways yet to be explored despite of the fact their well-known stress tolerance potential. Therefore, there is an urgent need to explore cyanobacterial metabolism under stress as well as their regulatory pathways to exploit them for sustainable agriculture. In recent decades the application of cyanobacteria has attracted the scientists because of uniqueness, better adaptability, and synthetic products.

Diverse cyanobacterial communities with the ability to fix atmospheric nitrogen together with their photosynthetic properties has demonstrated their application in the field conditions. Several cyanobacterial species thus have been exploited to enhance soil fertility, mitigate biotic and abiotic stress, and contamination management. The present book content has been designed to discuss the different aspects of cyanobacteria with an aim of helping in a better　understanding of advanced cyanobacterial molecular biology aspects to uncover the potential of cyanobacteria in tailoring of stress smart crops for the sustainable agriculture. Chapters have been designed to deal with the different aspects of cyanobacteria including their role in the evolution of life, cyanobacterial photosynthesis, stress-tolerant cyanobacterium, biological nitrogen fixation, circadian rhythms, genetics and molecular biology of abiotic stress responses.