In this activity, students investigate the fascinating and complex process of decomposition and lay the foundation for deeper understanding of concepts related to matter and energy transfer in ecosystems. Through exploration and discussion, students go beyond simple definitions. Instead, students discover key characteristics of decomposition as they struggle with creating a sequence for decomposing wood and leaves. They learn the difference between physical decomposition and chemical decomposition and that many things contribute to decomposition, but certain organisms are classified as decomposers. They also search for and discuss evidence of decomposers, make model diagrams to further develop their ideas about the process of decomposition, and discuss decomposition and its role in the cycling of matter. Finally, students are challenged to recognize the evidence and impact of decomposition in the ecosystems they explore.