A cross-section is a cut or slice through an object that reveals its internal structure. This technique is commonly used in fields like biology, engineering, and geology to provide a clear view of what lies beneath the surface. For example, a cross-section of a tree trunk shows its rings, which can indicate its age and growth conditions. In architecture, a cross-section can illustrate how different levels of a building relate to each other. By examining a cross-section of a building, architects can better understand the layout and design, ensuring that all elements work together effectively.