This book puts an updated account on functional aspects of multiphasic microbial interactions within and between plants and their ecosystem. Multipronged interaction in the soil microbial communities with the plants constitute a relay of mechanisms that make profound changes in plant and its micro-environment in the rhizopshere at physiological, biochemical and molecular levels. In agro-ecological perspectives, such interactions are known to recycle nutrients and regulate signalling molecules, phytohormones and other small molecules that help plant growth and development. Such aspects are described deeply in this book taking examples from various crop plants and microbial systems. Authors described the most advantageous prospects of plant-microbe interaction in terms of inoculation of beneficial microorganisms (microbial inoculants) with the plants in which microbes proliferate in the root rhizosphere system and benefit plants' with definite functions like fixation of nitrogen, solubilization and mobilization of P, K, Zn and production of phytohormones. The subject of this book and the content presented herein has great relevance to the agro-ecological sustainability of crop plants with the help of microbial interactions.