The ability to observe the world around us through sight provides us with many advantages we may take for granted daily. We are able to recognise a hazard well in advance because we see it; we can find allies because we see them. Further, thanks to the perception of the world that gives us sight, we can collect information to help us develop feelings, such as trust in others, love and sensations, like beauty. However, the mechanism to enjoy this capability is really complex, starting with the structure responsible for receiving, processing and transmitting information to the brain. This book discusses the ways in which ganglion cells are used in the nervous system, as well as its morphology, functional development and role in diseases.