A cell is the basic unit of structure and function in an organism. Cells are like bricks that make a building. Cells are the basic building blocks of organisms. Every organism is made of cells and every cell comes from another cell. This idea is called cell theory.
All cells are alike in some way.
A cell membrane is a thin layer that surrounds and holds that parts of a cell together. It is made of proteins and fats. The cell membrane controls the movement of material into and out of a cell. The nucleus contains a nucleolus and nucleoplasm. This material inside the nucleus controls the cell.