The light microscope was in my opinion the single most important invention for the field of life sciences, which enabled us to understand how living systems work. The idea of using glass to magnify objects is very old - the oldest lens was found in the archaeological excavations of the Assyrian city of Nimrud and is believed to have been made between 750 and 710 BC. It took about two thousand years (at least in Europe) to go from that rough piece of thick glass to glasses, which became widely used for eyesight correction in the XIII century. Finally, after another four hundred years, the first microscopes were made in the beginning of XVII century more or less simultaneously by the Dutch spectacle-maker Zacharias Janssen, the Dutch inventor Cornelis Drebbel and the famous Galileo Galilei, whose friend Giovanni Faber coined the term "microscope".
This invention was a bomb for the scientific and even general educated public of the time, and amazing discoveries started pouring from this horn of plenty. The English polymath Robert Hooke was the first to propose that living organisms are made of tiny compartments, which he saw when observing the cross-section of cork tree under a microscope and called cells. The Dutch Antonie van Leeuwenhoek became the "mad genius" in the field. Although his initial interest was in studying the structure of fabric to examine its quality for his draper shop, he soon developed a method to craft very small, round and smooth lenses. This enabled him to make an astonishing number of discoveries, ranging from the existence of microbes to the sperm cells and red blood cells. Since he did not want to share his secret with anyone, his discovery of single-celled organisms was received with suspicion at first, but in the end the scientific community had to accept his work, and he even became a member of the Royal Society.
In the following centuries, microscopes were perfected until they reached the absolute resolution limit of light microscopy, which we will cover in the first activity. They became widespread, with scientists applying them to study small animals, plant and animal tissue slices (histology), individual cells of multi-cellular organisms, single-celled eukaryotes and prokaryotes. A new era in microscopy began with the invention of fluorescence microscopy in the beginning of the last century, which will be the topic of the second activity. In the following decades, scientists used it to understand molecular details of the inner world of the cells, as well as their interactions and organisation within organisms. Furthermore, both conventional and fluorescence microscopy also became important medical tools, used to diagnose and monitor infectious diseases, cancer, neurodegenerative diseases and others. Nowadays, light microscopy, despite being about 350 years old, is still blooming, and novel approaches, which we will discuss in the last activity, continue to expand the boundaries of our knowledge.
Let's begin our journey by taking a little quiz, and you can retake it after you go through the activities.
What can you see in a light microscope?
- HIV virus particle
- Atoms of carbon in human cells
- Which neuron is active in the brain of a living mouse
- Two proteins interacting with each other
- Smallest cells in the world
The videos below relate to the activity sheets so download these first before watching.
Activity 1- The Resolution Limit of Light Microscopy - YouTube