Interest in the development of eco-friendly, green, cost-effective, and straightforward methods for the synthesis of nanomaterials. In green synthesis methods different materials from biological origin, including microorganisms, cells, plants, or their enzymes or extracts, are employed with the focus on a greener environment, minimizing generated waste, and implementing sustainable processes. The green synthesis of nanostructured material has an extremely captivating and challenging approach for all researchers, due to the presence of phytochemicals agents in the extracts, such as carbohydrates, flavonoids, saponins, proteins, amino acids, chromone, steroids, phytol, and terpenoids. The phytochemicals present in plant extracts play a key role in the improvement of reduction rate, size, and stabilization, by acting as good reducers, surfactants, structure directors, and capping agents. This book focuses on the green synthesis of nanomaterials with various biological systems, with particular emphasis on the mechanisms of nanomaterial synthesis, spectroscopic characterizations, and their applications in a variety of industry sectors. This will be an important reference source for materials scientist, bioengineers and environmental scientists.