What if you just keep zooming in?

Atoms measure about 0.1 nanometers, making them far too small for visible light, whose wavelengths range from 380 to 750 nanometers, to resolve; light simply diffracts around such minute structures. Utilizing electrons accelerated to high speeds produces wavelengths between 2 and 3 picometers, providing the precision needed to image atoms. Louis de Broglie's discovery that matter exhibits wave-like properties underpins this breakthrough, allowing electron microscopes to reveal the atomic world. The technological leap has transformed our ability to observe the basic building blocks of matter inside meticulously shielded environments.

Electrons accelerated by a tungsten filament achieve far greater resolution due to their shorter wavelengths compared to light. A specially designed coil with an iron gap produces a toroidal magnetic field that steers electrons through the Lorentz force, guiding them in a spiral path toward the center. This innovative design, rooted in de Broglie’s discoveries and refined by Ernst Ruska, led to the first operational electron microscope in 1931.

A basic TEM used a focused electron beam on ultra-thin samples, allowing electrons to pass differently through areas based on thickness and creating a detailed electron imprint. An electromagnetic lens then magnified this imprint onto a fluorescent detector to form the final image. Early limitations in magnification led to innovative experiments with additional lenses, culminating in magnifications over 10,000 times that enabled unprecedented close-up views of microscopic organisms.

Magnetic lenses in electron microscopy suffer from spherical aberration because electrons farther from the optical axis are over-deflected by the non-linear magnetic field, causing them to focus ahead of the central rays. Conventional optical systems correct this issue by pairing converging and diverging lenses, but the inherent two-pole structure of magnets forces all electromagnetic lenses to converge electrons, making a diverging correction impossible. Otto Scherzer’s discovery confirmed that a radially symmetric magnetic lens cannot diverge electrons, establishing a fundamental limit on further magnification improvements in electron microscopy.

In 1955, the field ion microscope provided the first accepted atomic image by shooting helium or neon atoms at a positively charged, atomically sharp needle tip, overcoming spherical aberration challenges despite only revealing the needle’s apex. This ionization technique, while limited in scope, marked a significant advance before electron microscopes expanded the frontiers of microscopic imaging. Modern technology mirrors this evolution, as persistent targeted ads and data tracking now intrude on personal privacy. Innovative services like Incogni empower individuals to challenge data brokers and efficiently delete unwanted personal information, reclaiming control over digital data.

Scientists transformed electron microscopy by replacing the random tungsten filament with a sharpened tip that extracted electrons for a narrow, thousand times brighter beam. This innovative beam, inspired by cathode ray tube technology, scanned nanoscopic samples piece by piece, leading to the first images of single atoms by 1970. Despite this breakthrough, the inherent challenge of spherical aberration remained an unsolvable limit to resolution.

Probe microscopes transformed atomic imaging by employing an incredibly small stylus that glided over samples to detect nanoscale forces and quantum variations. The method bypassed traditional optical limitations by avoiding lenses and the issues of spherical aberration, resulting in precise and three-dimensional surface maps. Although these devices effectively mapped structures by tactile sensation rather than visual capture, they marked a significant advancement in microscopy during the 80s and 90s.

Facing the inherent limits of radially symmetric lenses, Urban, Haider, and Rose boldly broke convention by intentionally disrupting symmetry to counteract spherical aberration. They engineered a lens system using hexapole electromagnets that first twisted the electron beam into a distorted triangular saddle with a slight central divergence, then reformed it into a nearly perfect circle with corrected aberration. Under immense time pressure and dwindling funding, a critical overnight pause allowed the magnets to settle, and at 2 a.m. the reengineered lens stabilized, revealing astonishingly clear atomic images. This breakthrough not only overturned decades of failed attempts but also pushed transmission electron microscopy resolution to an unprecedented 0.13 nanometers, stunning the scientific community.

A tiny lamella sample was prepared and precisely aligned in a transmission electron microscope to reveal atoms arranged like beads on a string. High magnification displayed atomic resolution in strontium titanate, clearly showing elements such as strontium, titanium, and oxygen, with slight carbon contamination observed. Aberration correction enabled accurate measurement and identification at the atomic level, a breakthrough recognized by the prestigious Kavli Prize and now essential for material science research.