After applying the principles of visual science to military reconnaissance and intelligence for many years, the author has prepared a tutorial integrating the many fundamental mechanisms underlying the visual capability found in the animal kingdom. He shows that multicolor vision has been found in the animal kingdom from the beginning (for at least 500 million years) and that vision is generally tetrachromatic. He shows that human vision follows this general plan, although its spectral performance is partially blocked by the absorption inherent in the lens of the eye. As a result, the human can be considered a blocked tetrachromat; in the vernacular but unscientifi cally, a trichromat. He provides an extensive series of circuit diagrams, from those defi ning the electrical performance of individual neurons, synapses and Nodes of Ranvier to complete diagrams integrating all of the major visual circuits of the eyes and the brain. The fundamental mechanisms and physiology associated with the photoreceptor cell of the eye are developed in detail, including the precise chemical composition of the four chromophores of vision. The concept of an ion-pump is defi ned in terms of the underlying electrostenolytic process for the fi rst time. It is shown that glutamic acid (glutamate) is the primary energy source powering the neural systems of all animals. The key elements of the midbrain involved in reading are described for the fi rst time. The book closes with a variety of fi gures describing the spatial and chromatic performance of the human visual system. Additional fi gures, an extensive glossary, an expanded tabulation of the parameters of the human eye, and more than 1000 references are available at the associated website, www.4colorvision.com.