There is little doubt that the immense current interest in visual development can be attributed to the tremendous impact of two of the early papers of Hubel and Wiesel (Hubel & Wiesel, 1963; Wiesel & Hubel, 1963) that were published only 1 year after their pioneering documentation of the functional characteristics of cells in the adult cat visual cortex (Hubel & Wiesel, 1962). In these next two papers, Hubel and Wiesel described the functional status of the neonatal kitten visual cortex prior to visual experience as well as some of the drastic consequences of early selective visual input on the functional properties of cortical cells. In so doing they pioneered experimental inquiry into the manner by which the visual response characteristics of cells in the adult visual cortex acquire their highly complex nature in early postnatal life. Hubel and Wiesel (1963) concluded that many of the visual response characteristics of cortical cells that they reported earlier in adult cats could also be recognized in the neonatal kitten cortex. Although there were very obvious differences between the status of the neonatal cortex and that of adults, Hubel and Wiesel were more impressed by the similarities between the two and concluded that certain functional characteristics of cortical cells were established crudely at birth under genetic instruction. However, the results of the second paper, which described the consequences of restricting patterned visual input to only one eye for several months, indicated that certain functional properties of cortical cells were also profoundly influenced by early visual experience.