Cells are the basic building blocks of life. They carry out essential functions that keep living things alive, like making energy, getting rid of waste, and communicating with other cells. All cells have three main parts: the cell membrane, the cytoplasm, and the nucleus. The cell membrane is like a gatekeeper, controlling what goes in and out of the cell. The cytoplasm is made up of water and other materials, like proteins and fats, that help the cell carry out its functions. And the nucleus contains the cell’s DNA, which tells the cell how to do its job.