Abstract
In this study, I clarified what tools and the place that enables children's expression in their play with natural materials in a yard. Also, focusing on a relationship between natural materials and tools, I examined expressions produced there. In play with water, sand, dirt, snow, and ice, where they tended to use tools, I found that characteristics of natural materials and tools sometimes determine an infants' expression. I tended to find expressions of "run", "accumulate", and "connect" in play with water, "put in", "accumulate" and "mix" in play with sand and dirt, "put in", "ram down" and "put on" in play with snow and ice. I described the necessity of grasping the tendency of tools necessary for each play and organizing an environment.
