Cells are the basic structural and functional units of all living organisms.2. Cells are typically very small; the smallest cells are about one-tenth the size of the head of a pin.3. Cells are composed of three major parts: the cell membrane, the cytoplasm, and the nucleus.4. Cells reproduce through a process of cell division, in which the nucleus of a parent cell divides into two or more daughter cells.5. Cells are capable of exchanging information and performing complex functions through the use of signaling molecules.