THE DISCOVERY OF CELLS: HISTORY - BIOLOGY - 2025

The discovery of cells marked, without a doubt, a before and after in the history of science, especially in the area of ​​biology and other related natural sciences. These important building blocks that make up all living organisms were discovered in the early 17th century, during the 1660s, to be more exact.

Although it may now seem very obvious to speak of cells as the fundamental units of living beings, before their discovery they were not had in the scientific panorama, nor was it thought, much less, that all organisms were composed of one or more of these.

Graphic representation of Robert Hooke's microscope (Source: Robert Hooke via Wikimedia Commons)

Perhaps it is pertinent to remember what we have known since the seventeenth century: that everything living on earth is made up of these small cells. From the thousands of microorganisms that colonize virtually every environment in the biosphere, to the macroscopic animals and plants on which we feed, they are made up of cells.

Although of different shapes, sizes and functions, the body of an adult human being has approximately 30 trillion cells, which are organized in the form of tissues that, in turn, make up organs and systems. The simplest organisms are made up of individual cells that spread by dividing into two.

Some branches of biology are in charge of the study of these structures with the main objective of knowing more about how they are constituted, molecularly speaking, and how they work in the construction of individuals as complex as multicellular animals and plants.

History

The first person to observe and describe cells was Robert Hooke, an English physicist who, in 1665, published a work known as "Micrographia", dedicated to microscopic observation and where he described his observations of a cut of a cork sheet.

In the Micrographia paper, Hooke referred to as "cells" or "pores" the hexagonal microscopic units, arranged in a manner similar to a honeycomb, that he evidenced under the lens of his microscope.

Although it was Hooke who introduced the term "cell" to science, the previous invention of the microscope had already set a precedent in the discovery of the microscopic world, and several scientists had made similar observations before:

-Athanasius Kircher, in 1658, had already shown that worms and other living creatures developed in decaying tissues.

-At the same time, the German naturalist Jan Swammerdam described red blood cells (erythrocytes) as blood corpuscles and stated that frog embryos were composed of globular-looking particles.

In 1676, the Dutch Anton van Leeuwenhoek, an amateur scientist with a passion for the microscopic world, declared before the Royal Society the existence of mobile microscopic organisms whom he called "animalcules", which today we know as protozoa and other beings unicellular.

Reconstruction of one of the microscopes made by Leeuwemhoek (Source: Jeroen Rouwkema via Wikimedia Commons)

Van Leeuwenhoek did not have a university education, however, he had recognized talents, not only as an observer and recorder, but also as a manufacturer of microscopes, with which he made his discoveries.

Animal cells and plant cells

More than a century after the exciting discoveries of Robert Hooke and Antoni van Leeuwenhoek in the early 1800s, scientists began to ask more questions about what made up the structures of animals and plants.

Thus, the German Theodor Schwann continued to study plant cells and Matthias Schleiden, another German scientist, began to study animals, realizing that like the first cells described by Hooke in the plant tissue of cork, these were also composed by cells.

The beginning of the Cell Theory

In 1831 Robert Brown, a Scottish botanist, by observing orchid leaf sections under the microscope, established that living cells had a structure within them that he called the "nucleus", stating that this was essential for their survival.

It was not until 1838 when both German scientists, Schleiden and Schwann, formally proposed that all living organisms on earth are composed of cells and it was this statement that gave rise to one of the first postulates of the now known "Theory cellular".

Schwann's exact words were “… the elementary parts of all tissues are made up of cells… there is a universal principle of development for the elementary parts of organisms and this principle is the formation of cells…”

Almost 20 years later, Rudolf Virchow, in the year 1855 realized that all cells come from a pre-existing cell that divides, that is, only cells produce other cells, as if they made copies of themselves.

Just as they were recognized as the elemental units of living organisms, cells were also considered by Virchow as the basic elements of pathological processes. Thanks to this conception, diseases began to be seen as cellular alterations in living beings.

Internal components of cells

Interest in the characteristics of cells increased with each discovery that was made public about it. Thus, shortly after the formulation of the cell theory, scientists realized that the interior of cells was not a homogeneous fluid, but quite the opposite.

Some investigators, after looking at it in some detail, described it as fibrillar, while others considered it to have a reticular, granular, or alveolar appearance.

The advent of better fixation and staining techniques allowed for more accurate descriptions, which led to the identification of the different structures contained within cells.

In 1897 the concept of the endoplasmic reticulum was introduced, while mitochondria were described in 1890 by Carl Benda. In that same year Camilo Golgi described the complex that today bears his name.

Walther Flemming coined the term chromatin when referring to ribbons that became evident during cell division, and in 1882, he called this division process "mitosis". Chromosomes were detailed in 1888 by Wilhelm Waldeyer by looking at metaphase, one of the stages of mitosis described by Flemming.

References

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