The ‘cell’ is the smallest structural unit of living matter that is capable of functioning independently. All basic functions for the organism survival take place inside cells. As bricks assemble to make a building, cells assemble to make the body of every organism. A group of cells form a tissue which performs a specific function. A group of tissue forms an organ and in the same way a group of organs form an organism. That is why cells are considered as the basic structural units of living organisms.