It’s the Little Things
As promised, we’re taking a break from AI to return to other science topics. This time, we look at how we look at tiny things.
Our light microscopes can see down to the mid nanometer range, but ones in the Scribes Series can see single-digit picometers. Here’s a refresher of the Greek prefixes:
-millimeter = thousandth of a meter (a grain of salt)
-micrometer = millionth of a meter (a mitochondrion in a cell)
-nanometer = billionth of a meter (10 hydrogen atoms lined up side-by-side)
-picometer = trillionth of a meter (when you slice a helium atom into 30 equal parts, each one is about 1pm wide)
I specify light because some microscopes use electrons. That kind sees tinier objects but has serious drawbacks that we’ll discuss in a bit.
Light Microscopes and Light Math
Light is made of photons, which behave as waves. Their wavelength determines how small of an object you can see. German physicist Ernst Abbe came up with a formula to figure out just how small. It’s etched on his monument:
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-Ulrikelovesscience, CC BY-SA 4.0, via Wikimedia Commons
Here’s a non-cursive version:
d = λ / (2n · sinα)
λ = wavelength of the light
d = resolution of the image you can see
n = refractive index of the lens (how much it slows and bends light)
α = maximum half-angle of light entering the lens (a bigger lens reveals smaller details)
So the smaller the wavelength, the smaller you can see. But there are limits. Let’s discuss the energy limit first.
As wavelength goes down, energy goes up. And when the energy gets high enough, two bad things happen:
1. Most of the light passes through the object without interactions. We generally see objects only when light bounces back to us from the object–a notable exception being fluorescence which absorbs and re-emits light.
2. The little bit of light that does interact will ionize atoms and harm living things. Light with the highest energy is a gamma wave–a form of ionizing radiation. (The bad kind: 
)
Additionally, gamma rays take a lot of energy to create, and regular lenses can’t reflect or bend them, making it impossible to focus or magnify the image. When gamma rays do strike an atom, they usually only interact with the nucleus, not the electrons surrounding it. That’s not helpful because it’s the electrons that define the shape of atoms, and, by extension, the things we see. I’m thinking of designing a Valentines Day card that says, “You have pretty electrons.” If I get enough requests, I’ll definitely do it!
Anyhow, when a gamma ray does strike an electron, it sends it flying in unpredictable ways, ruining the picture even more.
Here’s a quick refresher on the electromagnetic spectrum:
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-Jonathan S Urie, CC BY-SA 3.0, via Wikimedia Commons
The highest energy light we can use in microscopes is a hard X-ray, which is 0.1 to 0.01 nanometers or 10^-11 (at the border of x-ray and gamma in the chart above.)
Beyond energy problems, light also has a diffraction limit. Using Abbe’s formula, we find that visible light can only take clear photos down to around 200 nanometers. What do we mean by diffraction limit? Let’s unpack that.
Distracted by Diffraction
First, here’s a diffraction pattern:
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-Geek3, CC BY 3.0, via Wikimedia Commons
For those who remember old cartoons, this is not the background of the Looney Tunes title screen, though I can’t help but see Porky Pig poke his head out from the middle.
When a photon flies toward an object that’s almost as small as the photon’s wavelength, the photon will bend around the object. Send a stream of photons at the object, and each will diffract at slightly different angles, creating the bullseye pattern in the image above. This pattern is usually too small to see with the unaided eye.
Such diffraction poses no problem when illuminating large objects, because the patterns are small compared to the object you’re observing. But with tiny objects, these overlapping patterns can make the image blurry. You can’t tell if you’re looking at one atom or a group of them huddled together. This ability to distinguish between separate objects is a microscope’s resolution.
If you’d like a more mathy explanation, watch this short video:
Scientists have devised clever ways to bypass this diffraction limit of 200nm, letting us view images as small as 20nm. I might explain some of these techniques in a later newsletter, if you’d like. But researchers in Mallory’s world have found even better ways to break the diffraction limit, giving them clear images in the picometer range (1,000 times smaller than what our best light microscopes can see.)
By the way, diffraction happens for all kinds of waves, and not just when a wave bends around an object. Waves also diffract when they pass through a narrow gap:
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-Verbcatcher, CC BY-SA 4.0, via Wikimedia Commons
See how waves entering the narrow channel between the rocks become bow-shaped when they exit? That’s diffraction. And when the moon hits your eye without diffracting around it? That’s amore. In my version of the song, anyway.
What about Electron Microscopes?
Because electrons have shorter wavelengths than photons, they make smaller images. Visible light has a wavelength between 380 to 700nm, letting you see bacteria. But electrons often have a wavelength shorter than 1nm, letting you see viruses.
But electron microscopes only work in a vacuum. Any air would scatter the beam of electrons, ruining the image. And cause electrical arcing, burning out the filament. Both issues are why old CRT tv sets used vacuum tubes. Yet another old-timey reference. I just sent my daughter off to college and now I’m a codger. 
Because electron microscopes require a vacuum, samples must be dry to see them–any moisture will evaporate and break the vacuum. And living samples can’t survive the vacuum or the electron bombardment.
That last limitation is huge. It would help doctors to see tiny details inside patients in real time. Present medical imaging is severely limited. CT, MRI, and PET scans can only see down to about 1 to 3 millimeters. Ultrasound can see 50 to 500 micrometers, but, as the name suggests, that uses sound, not light. And it has its own list of drawbacks.
In Mallory’s world, where patients get nanobots injected into their blood stream, seeing microscopic things inside live patients is a must. Those bots carry cameras that see cellular abnormalities before they grow into tumors, letting them kill or correct cancer cells long before they metastasize and cause symptoms. And because this imaging is safe, cheap, and continuous, Mallory never goes to a doctor for imaging. She doesn’t soak up radiation, pay expensive medical bills, or wait days for images to be read. Must be nice. But that technology creates new problems. Read about them in Scribes’ Descent.
Is there any aspect of microscopy you’d like to hear more about? Reply and let me know.
References:
–https://www.quora.com/Why-cant-gamma-ray-microscopes-be-crea…
https://nysora.com/regional-anesthesia/topics/equipment/phys…
https://cpaimaging.com/2025/12/20/what-is-molecular-level-pr…
Writing update: I’m done with the first draft of Emolecipation episode 3 and am outlining episode 4. Moles are coming!
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