Fungi are an essential organism in human life. They play a vital role in medicine by yielding antibiotics, in agriculture by maintaining soil fertility, are consumed as food, and forms the basis of many industries. The chapter deals with the general study of fungi along with its basic structure and economic significance of fungi. It also provides information on the usefulness and harmful effects of fungi. Role of fungi in industries such as bakeries, breweries, mushroom cultivation etc. has been detailed. Bacteria are used in the manufacture of foods and production of antibiotics, probiotics, drugs, vaccines, starter cultures, insecticides, enzymes, fuels and solvents. Also, with genetic engineering technology, bacteria can be programmed to make various substances used in food science, agriculture and medicine. The importance of bacteria in different fields such as medicine, agriculture, industry etc. is discussed. Bacteria are essential in the production of many dietary supplements and pharmaceuticals.