Illustrate in detail about the Cell theory

All living organisms are composed of cells, and they are the basic structural and functional units of life, just like the atom is a fundamental unit in all chemical structures. This concept forms the basis for the "cell theory" proposed by M.J. Scllleiden and T. Schwann in 1838-34. They concluded that all plants and animals are composed of individual cells. The same concept is also applicable to microorganisms. Some organisms, e.g., the bacteria and protozoa are unicellular, while others are multicellular organisms, like fungi, plants and animals. Fungi are composed of individual cells of similar structure, while plants and animals are made up of different types of cells. Cells in all living organisms, whether unicellular or multicellular, show several common structural features, and many events in them are carried out in a similar fashion.