This book is the introduction to a series of e-books dedicated to the physiology and pathophysiology of neuroglia. The topic of neuroglia is generally overlooked in neuroscience curricula across the world, the main attention being focused on the description of excitability of neurons and neuronal networks. The neuroglia, being electrically non-excitable, are universally regarded as supportive cells which do not contribute to information processing. This oversimplified view, however, ignores the tremendous importance of brain homeostasis, which is imperative for the ongoing activity of neuronal networks. It also ignores the truth that specialization of neurons and their ability for rapid propagation and multi-level integration of signals become possible only because of delegation of homeostatic abilities to neuroglia. Furthermore, glial cells contribute to information processing as they can modulate neuronal synaptic transmission. Finally, neuroglia provide the only system of brain defense and as such these cells are intimately involved in all types of neuropathologies, and contribute to both neuroprotection and regeneration of the nervous system. The e-books in this series provide a platform for in-depth learning of all aspects of neuroglial cells function in health and disease.