A mesocosm is an experimental tool used in ecological and environmental research to replicate and study natural ecosystems under controlled conditions. It may take the form of a bottle ecosystem: a self-contained, miniature model of an ecosystem enclosed in a transparent container, such as a glass/plastic bottle or a mason jar. It is a simplified representation of natural ecological processes, demonstrating interactions among biotic (living) and abiotic (non-living) components in a controlled, enclosed environment.