"Is this a cell?"
Kana was looking at an electron microscope image. A gray world with intricate structure.
"It's a mitochondrion," Rei explained. "You can clearly see the cristae of the inner membrane."
Milia showed her notebook. "Resolution: 0.2 nm"
"Nanometers?" Kana was surprised. "We can see such tiny things?"
"Precisely because it's an electron microscope," Rei said. "The limit of optical microscopes is determined by light wavelength."
"Wavelength?"
"Visible light is 400 to 700 nanometers. You can't see anything smaller."
Kana thought. "But viruses and proteins are much smaller."
"Yes. That's why we use electron beams. Electron wavelength is about 100,000 times shorter than visible light."
Milia drew a diagram. Electron gun, lens system, sample, detector.
"Accelerate electrons and hit the sample," Rei explained. "Detect transmitted or reflected electrons."
"But why do electrons have wavelength?" Kana looked puzzled.
"De Broglie relation," Rei wrote the equation. "λ = h/p. Particles have wave properties."
"Quantum mechanics?"
"Yes. Electrons are both particles and waves. Their short wavelength allows us to see small things."
Milia showed another image. Ribosomes, protein complexes, DNA double helix.
"Beautiful," Kana murmured. "They really have this structure."
"But not in living state," Rei added. "Electron microscopes need vacuum. Samples are fixed and stained."
"Can't we see them alive?"
"Recently, cryo-electron microscopy has developed. Rapid freezing preserves nearly natural state."
Milia wrote in her notebook. "Cryo-EM: Nobel Prize 2017"
"Yes. It revolutionized structural biology," Rei said. "We can see protein tertiary structure at atomic level."
Kana stared at the image. "In this tiny world, there are life's secrets."
"Exactly. Enzyme active sites, receptor binding pockets, DNA base sequences."
"Everything depends on shape."
"Yes. Structure determines function. The central principle of molecular biology."
Milia showed another image. Cross-section of cell membrane.
"I can see the lipid bilayer," Kana pointed out.
"Dark layer and bright layer. Phospholipid heads and tails," Rei explained. "Hydrophobic tails inside, hydrophilic heads outside."
"Same as the surface tension we learned before."
"Everything connects," Rei smiled. "Chemistry, physics, biology. Electron microscopy shows their integration."
Kana drew in her notebook. "The invisible world becomes visible."
"But to see requires understanding," Rei said. "Why can we see. How do we see."
Milia nodded.
"Optical microscopes are simple but have limits," Rei continued. "Electron microscopes are complex but open new worlds."
Kana asked. "What's the difference between scanning and transmission?"
"Transmission electron microscopy TEM passes electrons through the sample. You see internal structure."
"Scanning electron microscopy SEM scans the surface with electrons. You see three-dimensional surface structure."
Milia placed both images side by side. TEM shows internal details, SEM shows surface topology.
"Choose based on purpose," Rei explained. "For organelles, use TEM. For cell surface or virus shape, use SEM."
Kana was impressed. "The world you see changes with the tool."
"Yes. Science evolves with tool invention."
Milia showed a note. "X-ray crystallography, NMR, cryo-EM"
"Each sees molecules from different perspectives," Rei said. "Integrate everything to approach truth."
Kana stared at the image. A gray world. But it contains information richer than color.
"The world seen by electron microscope," Kana murmured.
"True form invisible to human eyes," Rei answered.
Milia smiled. Technology to see the invisible world. That's the key to solving life's mysteries.