Viruses are the submicroscopic organisms that are parasitic in nature. Molecular virology refers to the scientific study of viruses on a molecular level. The genetic material of viruses is enclosed in a protein coat. The various aspects related to viruses are also studied under molecular virology such as their ways to infect and exploit host cells, their structure, evolution and classification, their interaction with host organism's immunity and physiology. The diseases caused by them, their use in research and therapy, and techniques to isolate and culture them are also studied within this field. Viruses can be classified either on the basis of the geometrical shape of their capsid or according to the host cell they infect. This book presents the complex subject of virology in the most comprehensible and easy to understand language. It is a compilation of chapters that discuss the most vital concepts and emerging trends in this field. This book attempts to assist those with a goal of delving into the field of virology.