Cell | Definition, Types, Functions, Diagram, Division, Theory, & Facts ...
Dec 1, 2025 · What is a cell? A cell is a mass of cytoplasm that is bound externally by a cell membrane. Usually microscopic in size, cells are the smallest structural units of living matter and compose all …
Structure and types of cells | Britannica
A single cell can be a complete organism in itself, as in bacteria and protozoans. Groups of specialized cells are organized into tissues and organs in multicellular organisms such as higher plants and …
What is a cell? | Britannica
Dec 10, 2025 · A cell is a mass of cytoplasm that is bound externally by a cell membrane. Usually microscopic in size, cells are the smallest structural units of living matter and compose all living things.
cell - Kids | Britannica Kids | Homework Help
Every organism, or living thing, is made up of structures called cells. The cell is the smallest unit with the basic properties of life. Some tiny organisms, such as bacteria…
Cell theory | Definition, History, Importance, Scientists, First ...
Nov 25, 2025 · First proposed by German scientists Theodor Schwann and Matthias Jakob Schleiden in 1838, the theory that all plants and animals are made up of cells marked a great conceptual advance …
Plant cell | Definition, Diagram, Model, Labeled, Characteristics ...
Dec 5, 2025 · A plant cell is the basic unit of all plants. Plant cells, like animal cells, are eukaryotic, meaning they have a membrane-bound nucleus and organelles. Their characteristic cell wall is …
Cell membrane | Definition, Function, & Structure | Britannica
Nov 27, 2025 · Enclosed by the cell membrane are the cell’s constituents, which include large, water-soluble, highly charged molecules such as proteins, nucleic acids, carbohydrates, and substances …
Eukaryote | Definition, Structure, & Facts | Britannica
Dec 8, 2025 · What is a cell? A cell is a mass of cytoplasm that is bound externally by a cell membrane. Usually microscopic in size, cells are the smallest structural units of living matter and compose all …
tissue - Students | Britannica Kids | Homework Help
The most basic unit in the hierarchy is the cell; groups of similar cells comprise tissues; groups of different tissues make up organs; groups of organs are integrated into organ systems; cells, tissues, …
Tissue | Definition, Types, & Facts | Britannica
Dec 1, 2025 · What is a cell? A cell is a mass of cytoplasm that is bound externally by a cell membrane. Usually microscopic in size, cells are the smallest structural units of living matter and compose all …