Link to other cytology web pages

Cells and the Microscope

Without the invention of the microscope cells would have remained an elusive unknown a black box of biology. Advances in biology often hinge on advances in technology. A variety of microscopes and other imaging devices have expanded our understanding of the sometimes subtle connection between structure and function in cells. The Cells Alive Site has an excellent tutorial covering some of the major advances in microscopy.

You should review the capabilities and major components of the following instruments:

  • compound light microscope
  • phase-contrast microscope
  • scanning electron microscope (SEM)
  • transmission electron microscope (TEM)

Follow this link to take a journey into the cell and discover the history behind the invention of the electron microscope.

For a microscopic comparison of plant, animal, and prokaryotic cells visit the University of Manitoba web site which examines subcellular organelles

The Cell Theory

Robert Hooke (2) was the first scientist to peer through a microscope and observe cells which are now considered the building blocks of life.

Figure 1

What Hooke saw, for the first time, was the cellular compartments of dead cork cells (see figure 1).

The statement by the German naturalist Lorenz Oken that "All organic beings originate from and consist of vesicles or cells." has come to be known as the Cell Theory.

Most texts credit plant biologist M. J. Schleiden and zoologist Theodor Schwann for proclaiming the cell to be the unit of life.

Another German scientist, Rudolf Virchow contributed to cell biology by proposing "omnia cellula e cellula" or every cell from a cell. This addition to the Cell Theory is called the biogenic law.

This law has a provision "under today's conditions" because scientists are aware of the possibility that a cell or cells could have developed spontaneously in the primitive conditions of ancient earth.

All cells (and organisms for that matter) at some time in their lives are capable of 6 operations which distinguish them from the nonliving world. These include:


Cellular operations

take in raw materials for food and growth


convert these materials into useful energy


use these raw materials to synthesize its own molecules


grow in an organized manner


respond to stimuli from the surroundings


replicate its genetic information and divide, forming 2 daughter cells



Modified July 8, 2005