The "Outer Layer" typically refers to the outermost part of an object or system. In various contexts, it can describe the surface of a physical item, such as the Earth's atmosphere surrounding the planet, or the protective coating on a product. This layer often serves to shield the inner components from external elements, such as weather or damage. In biology, the term can also apply to the outer layer of cells, known as the cell membrane. This membrane acts as a barrier, controlling what enters and exits the cell, thus maintaining its internal environment. The outer layer is crucial for protection and functionality in both natural and manufactured systems.