The observations of the English biologist and naturalist Robert Hooke, who discovered the cell

Cell Theory is the concept that the cell is the basic unit of structure in every organism. The theory was further developed after serious breakthroughs in microscopy (primarily made by the Dutch academic Antonie Van Leeuwenhoek) during the 17th and 18th centuries. This theory stands as one of the foundations of microbiology and biology itself, being a discovery of the highest importance.

Background and History

Before Cell Theory, scientists and commoners alike believed in the ancient principle of Vitalism, which originated from second century Rome and the acclaimed physician to the gladiators Galen. When conducting anatomical studies, Galen came up with the conclusion that living organisms were powered by some sort of a vital force or energy, a theory believed by

The Roman physician and surgeon Galen, who popularized and created the theory of vitalism

many until the publication of cell theory.

When Robert Hooke discovered the cell when examining a thin slice of cork using a simple, coarse compound lens in 1665, publishing his discoveries in the manuscript ‘Micrographia’, he made basic observations regarding cell structures, not truly identifying any of the organelles (which are the specialized subunits within cells that have specific functions), and mistaking the non-living cell walls for the cells themselves therefore not making proper observations. Nevertheless, his work helped inspire biologists to continue research in this field. Antonie van Leeuwenhoek’s drastic improvements in the field of microscopy allowed him to be the first to observe a cell itself, describing the appearance of the algae Spirogyra, and possibly also seeing a bacteria cell.

Developments and DiscoveriesEdit


Rudolf Virchow, the German pathologist and biologist known for completing cell theory

With so many developments in this curious field of science, the 1800s were ripe for innovation. Matthias Schleiden and Theodor Schwann developed the classical and original understanding of cell theory in 1839 publishing their results in the paper entitled ‘Microscopic Investigations on the Accordance in the Structure and Growth of Plants and Animals’. Their findings were considered to be revolutionary among the scientific community. Classical Cell theory was finally completed when Rudolf Virchow stated that all cells come from pre-existing cells after long periods of study regarding this matter 19 years later in 1858 in his paper ‘Vorlesungen über Cellularpathologie in ihrer Begründung auf physiologischer und pathologischer Gewebelehre’.

Classical InterpretationEdit

1. All living organisms are made up of one or more cells.

2. The cell is the basic unit of life.

3. All cells arise from pre-existing cells (and therefore reproduce).


The microscope used by Hooke to (incorrectly) observe a cell

Modern InterpretationEdit

1. The cell is the fundamental unit of structure and function in living organisms.

2. All cells arise from pre-existing cells through a process involving division.

3. Energy flow (metabolism) occurs within cells.

4. Cells contain hereditary information (genes that correspond to regions within DNA in the nucleus), which is passed down from cell to cell during reproduction.

5. All cells are nearly identical in chemical composition for organisms of a similar species.

6. All living things are made up of one or more cells.

7. Organisms composed of only a single cell are known as unicellular.

8. Organisms composed of a number of cells are known as multicellular.

9. The general physical and chemical activity of an organism depends on the total activity of independent cells.