Viruses are intracellular parasites that are found in all types of life forms, from plants and animals to prokaryotes and archaebacteria. These obligate infectious agents subvert various essential molecular and cellular processes of the host cell. Viruses exploit host cells to replicate and proliferate from cell to cell and from host to host, which leads to an increase in their own population within the host. Infection begins when viruses attach to the surface of the host cell. This means that the viruses bind to one or more cellular receptors, including proteins, carbohydrates and lipids. Viruses not only show the ability to evade immune responses to infect and replicate host cells, but also show the ability to control cellular stress responses such as degradation pathways, autophagy and cell death. Vector-borne viruses usually persist within the vector, but not on other hosts. Viruses often assemble within virus factories, but they can also mature and fold their surface and fusion proteins, depending on the endoplasmic reticulum (ER), Golgi apparatus, and subsequent extracellular pathways. This book is a compilation of chapters that discuss the most vital concepts related to the cell biology of viruses as well as virus-host interactions. It aims to serve as a resource guide for students and experts alike and contribute to the growth of the research on viruses.