History of the Electron Microscope

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Level 1: explained for kids, level 2: explained for the general public, level 3: expert. Scroll to the appropriate section.

Level 1: For Kids

Imagine a super powerful magnifying glass that can see things much smaller than anything else! A long time ago, people learned that tiny particles called electrons can be used to look at really small things, like the tiny pieces that make up everything around us. They found out that magnets can bend these particles and focus them, just like how a magnifying glass focuses light to make things look bigger. This discovery led to creating the first electron microscope, a special tool that lets scientists see things that are too small to be seen with regular microscopes—like tiny bugs that make you sick or the small parts inside cells.

Level 2: For the General Public

The electron microscope is a remarkable invention that allows us to see the tiniest details of the world, far beyond what the traditional light microscope can show. It started with experiments in the 1800s, where scientists found out that electron beams could be bent and focused using magnetic fields, similar to how light is bent with glass lenses in regular microscopes. Over the years, various scientists improved techniques to focus these electrons more precisely, allowing for clearer images. The first practical electron microscope was demonstrated in the early 1930s, showing that electrons could magnify objects to levels unmatched by light, leading to incredible advancements in science and technology, from biology to electronics.

Level 3: For Experts

The development of the electron microscope began with early observations by scientists like Plicker and Hittorf in the mid-19th century, who noted the effects of magnetic fields on electron beams in Geisler tubes, akin to the function of optical lenses on light rays. This foundational work was expanded upon by others, including Busch in 1922, who leveraged these properties to focus electron beams, aiding in the determination of the charge-to-mass ratio of electrons.

Significant advancements occurred with the work of Knoll and Ruska in the early 1930s, culminating in the creation of the first electron microscope. Ruska’s design used magnetic lenses to achieve a magnification previously unreachable, marking a pivotal shift in microscopic technology. The technique allowed for much higher resolution, leading to the electron microscope’s crucial role in scientific and industrial applications, from the study of viruses to the intricate inspection of semiconductor materials.

This transformative technology continued to evolve with the introduction of different types of electron microscopes, like the scanning electron microscope in the 1940s, which provided detailed topographical maps of samples. Innovations such as the development of the UV microscope and various types of cathodes have further refined the capabilities and applications of electron microscopy.

Understanding this history not only highlights the technological progress but also underscores the importance of interdisciplinary research in advancing our capabilities to explore the microcosmic aspects of the world. The Electron Microscopy Museum in Nürnberg aims to celebrate these achievements and inspire future innovations by preserving the rich history of this essential scientific tool.

A Really Comprehensive History

Early Observations of Electron Beam Focusing

The conceptual foundation of the electron microscope was laid in the mid-19th century, beginning with Plicker in 1858 (1,R7) and Hittorf in 1869 (2,R8). Both researchers independently observed that magnetic fields could deflect electron beams in a Geissler tube. Hittorf further discovered that an axially symmetric magnetic field could focus these beams, analogous to how a glass lens focuses light rays, due to collisions between the electron beam and gas within the tube. This focusing effect was independently described by Birkeland in 1896 (3,R9).

In 1922, Busch (4,R12) leveraged the imaging properties of axially symmetric magnetic fields to determine the charge-to-mass ratio of electrons. He focused the electron beams to a pinpoint by varying the current in the solenoid that generated the magnetic field, making the focus observable by projecting the image of an aperture onto a fluorescent screen. To aid in focusing, Busch added a wire cross to the aperture, which was then imaged onto the screen. His student, Wolf (5,R14), noted that only the center of the image was sharply focused and concluded that the uneven illumination was due to it being an emission image of the cathode.

Wiedemann and Wehnelt (6,R15) in 1898, and later Lenard in 1902 (7,R16), demonstrated the focusing capability of short coils relative to the electron beam path, suggesting that shorter solenoids could also effectively focus electron beams.

The Cathode Ray Oscillograph

Braun (8, R17) first utilized electron beams within a cathode ray tube to record rapidly changing electrical phenomena, laying the groundwork for the modern oscilloscope. To improve the visibility of small signals, Rankin (9, R18) used a short coil to image the anode aperture onto the screen, increasing the intensity of the writing spot. This concept was further developed by Flegler and Tamm (10, R39), who used two successive coils to demagnify the anode aperture image, enhancing the current density and the spot’s intensity. This innovation was pivotal in the development of the Transmission Electron Microscope (TEM) and the Scanning Electron Microscope (SEM).

Dufour (11, R22) in 1914 incorporated photographic film into the vacuum chamber of an oscillograph, enabling direct recording of the electron beam and pioneering electron microphotography within electron microscopes.

In 1928, under the leadership of Prof. Max Knoll (12, RP13), a team including Ernst Ruska, who later became a key figure in the development of the electron microscope, began enhancing the focusing capabilities of electron beams using magnetic and electrostatic fields. Busch initially observed the lens-like behavior of short magnetic coils, which could both magnify and demagnify images, similar to optical lenses.

In 1931, Ruska constructed an experimental setup using two magnetic lenses to investigate their magnification capabilities, using apertures with defined features such as metal mesh. Astonishingly, the quality of the magnified images was comparable to those produced by light microscopes, spurring further research into electron microscopy.

The UV Microscope and Electron Microscopy

The UV microscope, an intermediary development, utilized UV light, which has a shorter wavelength than visible light, enabling higher resolution. The application of UV light posed challenges due to focusing difficulties and the invisibility of UV light to the human eye. Early investigations into UV microscopes by Vladimir Zworykin, a key figure in the development of television and the SEM, utilized electron imaging of UV-sensitive photocathodes to enhance image brightness.

Zworykin also explored the amplification of electron images by focusing them onto metal surfaces, leading to the invention of photomultipliers and night vision devices. This research demonstrated the limitations of UV wavelengths with contemporary materials, although later advancements by companies like ASML facilitated the development of extreme UV microscopes used in modern microchip manufacturing.

De Broglie’s 1924 theory of matter waves, positing that electrons have shorter wavelengths at higher speeds, opened new avenues for microscopy, exceeding the magnification limits of optical microscopes.

The Invention and Advancement of the Electron Microscope

On June 3, 1931, Max Knoll presented early findings on electron magnification using magnetic lenses, marking the unofficial introduction of the electron microscope. Ruska and von Borries continued this work, demonstrating in 1932 that electron microscopes could produce images as sharp as those from light microscopes, with significantly higher potential magnification.

Developments in magnetic lens technology by Busch, Gabor, Ruska, and von Borries, including the invention of the iron-clad magnetic lens, were crucial. By 1933, these advancements led to the creation of electron microscopes capable of exceeding light microscope magnifications, with early models reaching up to 12,000 times magnification.

The commercialization of electron microscopy began shortly thereafter, with significant contributions from Ruska and von Borries, who joined Siemens to further develop and market the technology. The first commercial electron microscopes, equipped with advanced cathodes like the thermionic hairpin cathode, achieved magnifications of up to 300,000 times with film magnification.


The development of the electron microscope has been integral to advancements in numerous scientific fields, from biology to materials science. It has enabled us to see and understand the ultra-small structures of viruses and microchips, revolutionizing both health sciences and technology. The Electron Microscopy Museum in Nürnberg is dedicated to preserving and sharing this rich history, celebrating the achievements that have profoundly shaped our modern world.