Just what do children get out of inquiry? Good inquiry activities help students hone their inquiry abilities and teach them about the nature of science. But inquiry is also a way to teach science content, and teachers need to know if this instruction is helping children gain these important ideas. So, how do teachers know what students are learning? They should try a "Learning Log" a tool to help build knowledge from inquiry activities. This article describes a color and light activity the author did with first and second graders, and how a rubric for learning logs helped to make accurate judgments of what these students learned. However, learning logs can be uses effectively in any grade level and on many topics.