Microbial species isolated from extreme and pristine habitats are always diverse, which indicates biomolecules secreted by these species might have importance. A cure for disease is a desire considering the catastrophic situations that threaten the lives of humans and animals. Currently, the world is facing the health, social and economic, and diplomatic impacts of infectious communicable diseases caused by bacteria and viruses. It is a necessity to understand the huge microbial diversity residing everywhere with us in this world. Microorganisms are species that were born at the start of "life" and will stay after the end of all other forms of life in this world. This unseen majority has significant effects on the biogeochemical cycle as well as has numerous medical and non-medical applications. So, the ability of microorganisms to produce bioactive compounds and how they can be used in different fields, especially medicine and health care, have been discussed in this book.