Small science
How have microscopes revealed the tiny world around us?
Find out how microscopes reveal the invisible
What is the smallest thing you can see? A grain of sand? The lines of your fingerprints? Or perhaps, if you look really closely, the diameter of a human hair? Throughout most of human history, our eyesight was one of the biggest limitations on scientific research. Because we couldn’t see cells or bacteria or atoms, we had no concept of these things, and it wasn’t until the invention of the microscope in the 17th century that we started to understand the invisible world around us.
Scientists started to discover germs swarming in drinking water and miniature animals in lakes, and later they began to learn more about our own anatomy, finding taste buds and blood cells. Over the next century microscope technology boomed. Scientists worked to develop microscopes that were powerful enough to help diagnose cancer, seek out evidence at crime scenes, and, later in the 19th century, discover the building blocks of everything in our universe – atoms. From the humble beginnings of the simple microscope to the development of the first electron microscope, today we have far more advanced technology that can even view the space between atoms.
Microscopes are used to view and photograph very small objects that are invisible to the human eye. They can be categorised into two large groups: optical and electron. Optical microscopes are the ones you probably think of when you think of a microscope – they use a light source and a series of magnifying lenses so you can investigate your sample. This broad category is often used in diagnostic medicine and includes fluorescence microscopy, which observes fluorescence emitted by samples under special lighting, and laser microscopy, which uses laser beams to visualise samples.
Electron microscopes are even more complex, offering higher magnification and resolution. Instead of a beam of light, these pieces of equipment use a beam of electrons to create a projected image or record the bouncing back of electrons from the sample. There is also scanning probe microscopy, which includes atomic force microscopes that scan the surface of samples using a pyramidshaped probe to map the surface of the specimen.
“It wasn’t until the invention of the microscope in the 17th century that we started to understand the invisible world around us”
Why do We need electron microscopes?
When you are looking at something really small, if you have enough light your eyes can distinguish two points that are about 0.2 millimetres apart. This means the resolution of your eyes are about 0.2 millimetres. Light microscopes have much better resolution, and electron microscopes even more so. This is because electrons have much shorter wavelengths than white light, which has wavelengths of about 400 to 7,000 nanometres. The beams of electrons in an electron microscope are nearer 0.1 nanometres. The smaller wavelength means less diffraction of
light being scattered in random directions and as a result a less ‘fuzzy’ and more precise image is observed.
As scientists learn more and more about the microscopic world and our technology gets smaller, many structures of interest to research and development cannot be observed with light microscopy any longer. We require higher power and higher resolution to create things such as the tiny microchips inside our smartphones, and electron microscopes are becoming more popular.
microscopes in diagnostics and crime scenes
While technology relies on electron microscopes, many fields of biology are reliant on optical microscopes, particularly when it comes to identifying disease. Researchers use optical microscopes in diagnostics to observe samples. This is because diseases often leave a path of specific changes to the cells that can give a clue to what is happening to a patient, like the trademark dark dots inside malaria-infected cells, or the big gaps between brain tissue infected with bovine spongiform encephalopathy (known as BSE, or the infamous ‘mad cow disease’).
Optical microscopes are also utilised a lot in the field of forensics, where investigators diligently search for even the tiniest clues left at a crime scene and need to magnify evidence such as fingerprints or fibres from clothing.
the future of microscopes
There are many ideas and inventions that were created over the last decade that are still being developed for use in industry. At the forefront of pioneering work to improve microscope technology is the University of Manchester. Teams there have helped to develop a recordbreaking optical microscope that has brought biologists a step closer to being able to view live viruses (which currently can only be viewed under an electron microscope). Another project, launched in 2013 by the University of York, aims to combine the technology from optical and electron microscopes into one system in an attempt to overcome the challenges associated with both types.
It might be hard to predict the technologies of the future that are yet to be constructed, but one thing we can be certain of is microscopes haven’t yet reached their full potential. Who knows what else we will discover?
“A high-voltage electricity supply powers the cathode, which generates a beam of electrons”