Book excerpt: The present book Microbial Synthesis of Nanomaterials is written mainly for the public's acquaintance with the synthesis and characterisation of different types of nanomaterials (NMs) and their sustainable applications in various fields. The nano-era began the late 1990s, after which the production of NMs increased rapidly and is expected to reach 1.663 million tons by the end of 2021. Recent findings have shown that NMs play a vital role in various fields like agriculture, food industries, environment, medicine and pharmaceutical, electronics, and so on. Microorganisms play a key role in the formation and transformation of nanoscale minerals in the environment. These natural processes can be harnessed for the green synthesis of nanomaterials for a diverse array of commercial, industrial and environmental applications, presenting a sustainable alternative to more traditional physiochemical synthesis routes. This new book consists of 15 chapters which provide comprehensive knowledge about the synthesis of NMs and offer a critical overview of the current understanding of nanoparticle synthesis using microbes, covering NMs' synthesis, characterisation and applications, and providing discussion on future prospects. The editors believe that this book will be helpful to researchers, the scientific community, academicians, business farmers and policy makers. The editors thankfully acknowledge the financial support of the Russian Foundation for Basic Research, project no. 19-05-50097 and of the Ministry of Science and Higher Education of the Russian Federation within the framework of the state task in the field of scientific activity (no. 0852-2020-0029).