The first two years of life are characterized by considerable change in all domains – perception, cognition, action, and social interactions. Here, we consider the statistical structure of visual input during these two years. Infants spanning the ages from 1 to 24 months wore body-mounted video cameras for 6 hours at home as they engaged in their daily activities. Our data strongly suggest that the statistical structure of the learning environment is dynamic and ordered. The available visual statistics are not stationary, but rather they are gated by young children's developmental level. We find a rolling wave of "See-Saw" patterns over developmental time in two classes of important social stimuli: First faces, then hands; and within hands, first other-then-self-then-touching-then-holding. These ordered environments may help learning systems “start small,” find the optimal path to the optimal solution, and determine the architecture of the system that does the learning.