Density stratification refers to the layering of substances, such as liquids or gases, based on their density. In a fluid, denser materials sink to the bottom while lighter materials rise to the top. This phenomenon is commonly observed in oceans, lakes, and even the atmosphere, where different layers can have varying temperatures and salinities. In the ocean, for example, cold water is denser than warm water, leading to distinct layers. Similarly, in the atmosphere, warm air rises above cool air, creating a stratified structure. Understanding density stratification is essential for studying ocean currents, weather patterns, and ecological systems.