The fungi as microbe is present everywhere; in mountains and soil crust; in water and water bodies like rivers, oceans, lakes, ponds and glaciers; on plant surfaces, food grains, fruits and vegetables; on de-composting materials; on fabrics and leather in damp weather; air cooling systems; in environmental air outside and inside homes; on animals and human body parts etc. The well develop fungal growth can be seen with naked eyes on some of the material, while the fungal structures are only visible in microscope. These fungal microbe are harmful as pathogens to cause diseases in crop plants, food product, fruits and vegetables, in human being, animals, birds and marine wealth etc. However, some of the fungal species are beneficial to mankind, agriculture and environment. These are sources of food products, antibiotics, enzymes, organic acids, plant nutrient supplier, composting agents, biological control agents and so on. Most of us are unaware of all these facts about this fungal microbe, as this knowledge is not yet passed on to the generations although they play important role in our life at one or other point of time. It is a high time for all of us to know about this fungal microbe and the role they play in our life. Contents: Section I: An Introduction to Fungi 1. The Fungi and its Life 2. The Habitat of Fungi Section II: Fungi Harmful to Living Being 3.Fungi Causing Disease in Plant and Food Product 4. Fungi Causing Diseases in Human Beings 5. Fungi Causing Diseases in Animal 6. Fungi Causing Diseases in Birds 7. Fungi Causing Diseases in Aquatic Animal/Fish Section III: Useful Fungi 8. Fungi Useful in Industrial Production 9. Fungi as Biocontrol Agent 10. Fungi Used as Biofertilizers 11. Fungi Used as Decomposer 12. Fungi Used in Antibiotics Production About the Author: Suresh G. Borkar: Former Professor and Head , Department of Plant Pathology, Mahatma Phule Krishi Vidyapeeth , Rahuri, Maharashtra, India