This book combines classical fundamental knowledge with the latest advancements in fungal, bacterial, and viral systematics. It provides detailed information on the morphology, life cycles, and economic uses of fungi, with a particular focus on the biological activities of microbial products. These products include a range of drugs, such as antibiotics and medications for high blood pressure. While viruses, bacteria, and fungi often cause diseases and can be easily confused, they are fundamentally as different as a mouse is from an elephant.