A cell is a basic unit of life, and it is considered a structural and functional unit of an organism. Robert Hooke (1665) discovered the cell. Leeuwenhoek (1674) first observed the animal (living) cell and used the term “Animalcule” for it.
Matthias Schleiden examined a large number of plants. He concluded that all plants are made up of different cells that make tissue.
Theodore Schwann studied different types of animal cells and plant tissue.
He concluded that animal cells have a thin outer layer, which is today known as the plasma membrane.
Matthias Schleiden and Theodore Schwann jointly proposed cell theory in 1839. Its main features are as follows
(i). All living organisms consist of cells and their products.
(ii) All cells are structurally and metabolically similar.
(iii). Cells perform vital activities of an organism.
(iv) Each cell is a unit of heredity.
New cell arises from pre-existing cells “Omnis cellula-e cellula.” It is called cell lineage theory. This concept was given by Rudolf Virchow (1855). Rudolf Virchow gave the final shape to the cell theory.
Singer and Nicolson gave the concept of the fluid mosaic model.