Book excerpt: The study of viruses is known as virology. It focuses on the structure, evolution and behavior of viruses. Studying them is vital, as they cause various infectious diseases like dengue, yellow fever, smallpox, etc. The classification of viruses is done on the basis of the host that they infect, like fungal viruses, bacteriophages, animal viruses, etc. This book attempts to assist those with a goal of delving into the field of virology. Coherent flow of topics, student-friendly language and extensive use of examples make this textbook an invaluable source of knowledge.