Neurons in the visual system respond to specific features of the visual scene in their receptive fields. The receptive field, characterized by its position, size, orientation/direction selectivity, spatial/temporal preference and ocular dominance, arises from selective and precise wiring between neurons. In this talk, I will present two discoveries that we have made in the functional study of receptive field development. First, we have studied the roles of the molecular guidance cues ephrins and structured activity in the development of retinocollicular maps. By studying the overall structure of the retinotopic maps with intrinsic signal imaging, comparing the experimental data with a computational model, and determining receptive field structures in several lines of mutant mice, we have revealed the contributions of ephrin-As and activity- dependent mechanisms in retinocollicular map formation. Second, we have demonstrated that activity-dependent changes induced by normal visual experience during the well-studied critical period serve to match eye-specific inputs in the visual cortex, thus revealing a physiological role for critical period plasticity during normal development.