Can You Keep Zooming In Infinitely?

Atoms are over 3000 times smaller than visible light wavelengths (380-750 nanometers), with atoms measuring only 0.1 nanometers. Light diffracts or bends around objects much larger than its wavelength, making direct observation impossible.

In 1924, French physicist Louis de Broglie demonstrated that matter has wavelike properties, not just light. The wavelength of any object equals Planck's constant divided by its momentum (mass times velocity).

Electrons are better candidates than light for viewing atoms. When accelerated to 300 kilovolts (80% the speed of light), electrons achieve wavelengths of 2-3 picometers, over 100,000 times smaller than visible light.

This theoretical breakthrough opened the possibility of achieving 100,000 times more resolution than optical microscopes, potentially allowing direct visualization of individual atoms.

Hans Busch proposed using electromagnetic lenses to focus electrons in 1926. Ernst Ruska, a young PhD student, built the first prototype by coiling wire and surrounding it with iron, creating a donut-shaped magnetic field.

• Electrons boiled from a tungsten filament are accelerated through a positively charged anode • The magnetic field exerts Lorentz force on electrons, creating spiraling motion toward the center • This focuses the electron beam, similar to how optical lenses focus light

By 1931, Ruska and colleague Max Knoll built the first working electron microscope from brass. The focused electron beam passed through thin samples (100 nanometers), creating electron imprints detected by fluorescent screens.

Early versions barely magnified and weren't better than optical microscopes. However, Ruska persisted, adding multiple lenses. By the mid-1930s, the transmission electron microscope (TEM) exceeded 10,000x magnification and could image insects, bacteria, and viruses.

Otto Scherzer proved in 1936 that electromagnetic lenses had an unavoidable flaw: the magnetic field is much stronger near magnet edges than the center, causing electrons at the periphery to focus before central rays.

This spherical aberration occurs because the actual magnetic field doesn't scale linearly with distance from the optical axis. Outer electrons receive too much deflection, creating a blurred focus spread across the axis instead of a single point.

• Every magnet has two poles (North and South) - you cannot have just one • All magnetic field lines must start at one pole and end at the other, forming closed loops • This fundamental property makes it impossible to create a diverging magnetic lens to correct the aberration

Scherzer's theorem proved diverging radially symmetric magnetic lenses are impossible. This stopped TEM advancement for decades. By 1955, another technology (field ion microscope) took the first generally accepted atomic image, leaving the electron microscope development stalled through the 1980s and 1990s.

Albert Crewe replaced the tungsten filament with a sharper electric field source, creating a beam over 1000 times brighter. He combined this with cathode ray tube TV technology to scan electrons across samples bit by bit, creating the scanning transmission electron microscope (STEM).

By 1970, Crewe achieved the first image of single atoms using the electron microscope. This breakthrough inspired rapid adoption, producing countless atomic images and reviving decades of stalled progress.

Probe microscopes emerged that could image atoms by gliding a tiny stylus across samples, detecting quantum effects or nanoscale forces. These avoided spherical aberration entirely and produced 3D images, but they were sensing atoms rather than truly seeing them.

Despite improvements, spherical aberration remained the fundamental limit on TEM resolution. Even Crewe abandoned attempts to overcome it after over ten years of work. Throughout the 1980s-1990s, probe microscopes were the only option for atomic-level imaging.

Knut Urban, Max Haider, and Harold Rose realized that Scherzer's theorem only applied to radially symmetric lenses. If they deliberately broke the symmetry with an asymmetric lens, they might create a small diverging region that could correct spherical aberration.

• They used hexapole, octopole, and decapole magnets with bumpy magnetic fields and multiple coils • Electrons passing through a hexapole twisted into a triangular saddle shape, creating concave curvature in the middle • This opposite curvature could theoretically counteract spherical aberration from the main lens

They forced the distorted beam through a second hexapole working the opposite way, unbending the image back to circular shape. If mathematics and engineering aligned perfectly, the remnant divergence would cancel the spherical aberration.

With only weeks of funding remaining and the lens still on the drawing board, they completed it by July 23, 1997. After allowing magnets to settle for 24 hours, they switched on the equipment at 2 a.m. on July 24 and achieved perfect clarity—no aberration, only beautiful clear atomic images. After 60 years of failed attempts, the impossible was accomplished.

Urban, Rose, and Haider reduced TEM resolution to 0.13 nanometers, transforming average TEM images from blurry to stunningly sharp atomic-level clarity. Shortly after, Ondrej Krivanek independently achieved the same breakthrough for the scanning TEM variant.

Initially relegated to a small back room at a microscopy conference, word quickly spread about the results. Hundreds gathered outside, lining up to see the sharp images. In 2020, all four scientists received the prestigious Kavli Prize in Nanoscience.

• Material science and materials engineering require atomic-level observation to relate material properties to structure • Chemical engineering depends on seeing atomic-level processes • Without aberration correction, researchers only have half the information needed

Aberration correction became a game changer for electron microscopy. Today, every major university has access to similar microscopes, making atomic-level visualization routine rather than impossible. The technology transformed from 60 years of failure to becoming an essential research tool.