The concept of cells has been around since ancient times, but it wasn’t until the late 17th century that scientists began to understand their true nature. Discoveries made over several decades eventually led to the development of the cell theory, which is now a fundamental principle of biology. Let’s take a closer look at some of the key discoveries that paved the way for this theory.

Robert Hooke’s Microscope Observations

In 1665, Robert Hooke published his book “Micrographia,” which included detailed drawings and observations made using a microscope he had designed. Among other things, Hooke examined thin slices of cork and described the tiny, empty spaces he saw as “cells.” While he didn’t fully understand what these structures were, his work paved the way for further investigation into the nature of cells.

Anton van Leeuwenhoek’s Discoveries

Around the same time as Hooke’s work, Dutch scientist Anton van Leeuwenhoek was also making important discoveries with microscopes. He was able to observe living cells in samples of pond water and even discovered single-celled organisms such as bacteria and protozoa. His work helped to establish that cells were not just structural units but could also carry out complex functions.

The Work of Matthias Schleiden

In 1838, German botanist Matthias Schleiden proposed that all plants were made up of cells. He arrived at this conclusion after studying plant tissues under a microscope and observing that they were composed of individual units similar to those seen in cork by Hooke. This was an important step forward in understanding the fundamental building blocks of living organisms.

The Contributions of Theodor Schwann

Around the same time as Schleiden’s work, German physiologist Theodor Schwann was studying animal tissues under a microscope. He proposed that all animals were also made up of cells, and that these cells were the basic units of life. Schwann’s work, combined with Schleiden’s, led to the development of the cell theory.

The Cell Theory Takes Shape

In 1855, German scientist Rudolf Virchow proposed that all cells arise from pre-existing cells. This idea completed the cell theory, which states that all living organisms are composed of one or more cells, that cells are the basic units of life, and that all cells arise from pre-existing cells.


Thanks to the contributions of many scientists over several centuries, we now have a solid understanding of what cells are and how they function. From Hooke’s initial observations to Virchow’s completion of the cell theory, each discovery built upon those that came before it. Today, we continue to learn more about these fundamental building blocks of life and their role in everything from disease to evolution.