A terrarium is a glass container that houses soil and plants in an environment different from the surroundings. It is often a sealable container but can also be open to the atmosphere. Terrariums create a controlled environment that favors plant growth, often mimicking tropical or moist habitats. Closed terrariums have transparent walls that allow heat and light in, supporting photosynthesis and creating a miniature water cycle inside where moisture evaporates, condenses on the container walls, and returns to the soil and plants. Open terrariums are not sealed and suit plants that prefer drier conditions. Terrariums originated as Wardian cases in the 19th century, created by Nathaniel Bagshaw Ward to transport plants safely over long distances. Today they are popular as ornamental items and indoor miniature ecosystems that require minimal maintenance and space. In summary, a terrarium is essentially a miniature garden or ecosystem enclosed in a glass container, designed to sustain plant life in a controlled, often self-sustaining environment. Closed terrariums mimic humid, tropical conditions, while open terrariums are better for drier-loving plants. They are both functional and decorative indoor plant displays.