The Maker Movement has been received by the field of K--12 education with great enthusiasm as a way of teaching STEM content to children. We call attention to and identify learning opportunities in children's projects created in a playful, informal environment with easily available materials. In keeping with research in the field of maker education and learning sciences, we describe tinkering as a constructionist learning activity in which meaning making is captured through transitional objects (Bamberger, 1995). First, we examine one specific tinkering project and identify transitional objects within the project. Next, we discuss the process of meaning making as captured through the transitional objects and identify the significance of children's emerging views of scientific concepts. Finally, we discuss implications for adopting the concept of transitional objects for capturing children's meaning making and learning in the domains of K--12 science and engineering education.