Robert Hooke was the initial scientist to describe cells and he also came up with the term. Anton van Leeuwenhoek was the first to describe bacteria and protists.
We are all made up of cells. They are the fundamental units of you, me, an elephant, a shark, a snake, a cockroach, an oak tree, the mold growing on stale pizza, as well as the amoeba and all its single-celled relatives.
However, when you observe an elephant, we don’t observe any cells. We see greyish-brown wrinkly skin, large floppy ears, and the beast’s impressive trunk. We don’t see these cells because our eyes simply can’t see things at such a small scale.
The tiniest cell is a bacterial cell, measuring about 0.1 nanometer (10-9), while the average cell of an animal is generally between 20 micrometers and 100 micrometers. The smallest objects that our naked eyes can see are about 0.1 millimeters.
So, if cells are essentially invisible to us, who discovered them—and how?
A Short Background Of The Microscope
The history of the cell, and all microscopic life, is closely linked to the invention of the microscope.
Humans have long been aware that objects can be magnified when viewed through certain materials. By the thirteenth century, lenses had been invented and had been utilized in spectacles, magnifying glasses, and the telescope.
Microscopes came into the picture much later, in the early 17th century. Credit for the invention of the first compound microscope goes to a father-son duo, father Hans Janssen and son Zacharias Janssen. Sometime between 1590 and 1600, these spectacle makers in Holland had the idea of placing a lens on either side of a tube. Voila, the compound microscope was born.
Interestingly enough, ten years later, in 1610, Galileo Galilei decided to look through his telescope from the wrong end, thereby creating his own compound microscope, even though he didn’t know about Janssen’s work.
Galileo wasn’t afraid to take risks
Although scientists now had a microscope, it would take another 60 years or so before actual cells were discovered. The first reason was that these early microscopes didn’t offer much magnification; they only enlarged objects by 3 to 9 times, not enough to see a cell.
The second reason was that people weren’t searching for cells. The prevailing belief before microorganisms were found was that all life could be seen by the naked eye. With such a belief, many naturalists focused on describing large objects and their components.
The Discovery Of The Cell – Robert Hooke And Anton Van Leeuwenhoek
The credit for discovering the cell goes to legendary scientist Robert Hooke.
Robert Hooke, a native of the Isles of Wight in England, was a polymath and prolific scientist. He began his career as a mechanical engineer and inventor. He perfected the air pump, invented the spring balance for watches, and found a way to accurately determine longitudes at sea (although he curiously didn’t publish the result). He also assisted in rebuilding London after the Great Fire of London—no small accomplishment!
Robert Hooke and Isaac Newton were both interested in gravity. Hooke accused Newton of stealing his inverse square law after Newton published Principia. This caused a rivalry between the two, resulting in angry letters and professional sabotage. While Hooke didn’t gain fame for gravity, he became famous for his discovery of cells.
In 1665, Hooke published Micrographia, a book focused on the microscopic world. He created a compound microscope that magnified objects up to 50 times, allowing him to observe things smaller than ever before. Hooke made around 60 observations using his microscope, including bread mold, linen, silk, wild oats, and cork. It was while observing cork that he noticed its pores resembled the cells of monks, leading him to coin the term “cells.”
Micrographia was the first book to describe the smallest aspects of life and was very popular. Another scientist, Anton Van Leeuwenhoek, likely came across Hooke’s book. Leeuwenhoek, a textile merchant, had a unique microscope that magnified objects up to 250 times. He sent letters of his observations and experiments to the Royal Society, of which Hooke was a member.
In 1676, Leeuwenhoek examined a three-week-old pepper soup under the microscope and discovered “very wee animals,” which were the first written account of bacteria. He also examined the gunk on his teeth and found more of these tiny animals, which he called “animalcules.” Hooke later confirmed these findings.
The idea of cells and bacteria was considered outlandish in the 17th century when many scientists believed life came from thin air and that a mini-human existed in sperm. Today, the concept of cells is ordinary, but it was revolutionary at that time.
Around two centuries passed before the following group of scientists validated the concept of cells and made significant progress. During this period, the well-known saying in cell biology, “Omnis cellula e cellula,” which translates to “every cell comes from another cell,” was also introduced. The originator of this phrase, whether it was François-Vincent Raspail or Rudolf Virchow, remains uncertain.
Cell Theory was proposed by two scientists, Mattais Schleiden and Theodore Schwann, who built upon the work of previous scientists.
- All organisms are composed of cells.
- Cells are the fundamental building blocks of life.
- All cells originate from preexisting cells.
Modern scientists would not find the statements above surprising, but just a few centuries ago, the concept that the same components make up an elephant, humans, plants, insects, and even mushrooms in the forest was revolutionary!