Discovery of living cells would have been difficult, if not impossible, before Zacharias Jansen of the Netherlands invented the com­pound microscope in 1590.

Robert Hooke of England used the term cell to describe the cavi­ties he saw in sections of cork. In 1665, Hooke published a description of cork cells based on a study done with his improved compound microscope.

In 1839 Matthias Schleiden, a German bota­nist, and Theodor schwann, an animal anato­mist, formulated the cell theory, which set forth the concept that “the elementary parts of all tissues are formed of cells in an analogous, though very diversified, manner, so that it may be asserted that there is one universal principle of development for the elementary parts of organisms, however different, and that this principle is the formation of cells.”

The word cell comes from the Latin cella meaning small chamber. In biology, particu­larly animal biology, the term cell refers more specifically to the individual units of living structure rather than the compartments that may contain them. There actually are no compartments as such in most tissues (with the exception of bone and cartilage), but the living units, cells, are found in groups in which mainly adjacent cells restrain individual cells. As early as 1772, Corti observed thejellylike material in the cell that later was called protoplasm.