[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Histology](https://durgical.com/en/histology/) › [Methods and stains](https://durgical.com/en/histology/#a-methods) › Electron microscopy: what it shows that light can't

[Histology](https://durgical.com/en/histology/) · [Methods and stains](https://durgical.com/en/histology/#a-methods)

# Electron microscopy: what it shows that light can't

- Technique

It uses electrons instead of light and shows structures far smaller than light can, such as membranes, ribosomes and the inside of cilia.

Updated 2026-11-01

**See it in 3D:** [Kidneys](https://durgical.com/en/anatomy/kidney/) · [Main bronchi](https://durgical.com/en/anatomy/right-main-bronchus/)

## Key points

- Resolution: light microscope about 200 nm, electron microscope close to 1 nm.
- TEM = inside, ultrathin sections; SEM = surface in three dimensions.
- Minimal change disease is diagnosed only by foot-process effacement on TEM.
- Primary ciliary dyskinesia: dynein-arm defect seen on TEM.

## What it is

Electron microscopy resolves objects about 1 nanometre apart, against about 200 nanometres for light microscopy. Transmission EM (TEM) shows the inside of the cell in ultrathin sections; scanning EM (SEM) shows surfaces in relief. Clinically it is decisive in kidney biopsies, cilia, some tumours and viruses.

## Key facts

- Usual fixation: glutaraldehyde followed by osmium tetroxide, which preserves and contrasts lipid membranes.
- Embedding in epoxy resin and ultrathin sections tens of nanometres thick.
- Contrast with heavy-metal salts (lead, uranium): the image is black and white.
- Electron-dense = dark (binds much metal); electron-lucent = pale.

## Structure

- On TEM the cell membrane appears as a trilaminar line (dark-light-dark).
- RER appears as flattened cisterns studded with ribosomes; the Golgi as stacked curved sacs with vesicles.
- Mitochondria show a double membrane with inner cristae; lysosomes appear as dense bodies with mixed contents.

## What electron microscopy adds

| Ultrastructural finding | Where | Meaning |
| --- | --- | --- |
| Diffuse effacement of podocyte foot processes | Renal glomerulus | Minimal change disease (near-normal on light microscopy) |
| Subepithelial or subendothelial electron-dense deposits | Glomerular basement membrane | Immune-complex glomerulonephritis |
| Thinned or split glomerular basement membrane | Renal glomerulus | Alport syndrome and thin basement membrane disease |
| Missing or defective axonemal dynein arms | Respiratory cilia | Primary ciliary dyskinesia |
| Birbeck granules (tennis-racket shaped) | Langerhans cells | Langerhans cell histiocytosis |
| Dense-core neurosecretory granules | Tumour cells | Neuroendocrine origin of a tumour |
| Abnormal cristae or increased mitochondria | Muscle | Mitochondrial disease |

## Memory aid

Where light runs out, electrons take over: if H&E looks normal but the kidney leaks protein, think TEM.

## Test yourself

Think of the answer, then tap the question to see it.

## Which electron microscopy finding defines minimal change disease?

Diffuse effacement of podocyte foot processes, with glomeruli that look almost normal on light microscopy.

## What does it mean that a structure is electron-dense?

It holds a lot of the heavy-metal contrast and blocks electrons, so it looks dark.

## Which tennis-racket shaped structure identifies Langerhans cells?

The Birbeck granule, seen with electron microscopy.

## Why does the electron microscope resolve more detail than the light microscope?

Electrons have a much shorter wavelength than visible light, so objects about 1 nm apart can be separated.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/histology/electron-microscopy-what-it-shows-that-light-can-t/)

## See it in 3D

The structures of Durgical's 3D anatomy where it is found.

- [Kidneys](https://durgical.com/en/anatomy/kidney/)
- [Main bronchi](https://durgical.com/en/anatomy/right-main-bronchus/)

## Related

- [Microscopy and stains: H&E, PAS, trichrome, silver, immunohistochemistry](https://durgical.com/en/histology/microscopy-and-stains-h-y-e-pas-trichrome-silver-immunohistochemistry/)
- [From biopsy to slide: fixation, sectioning, frozen section](https://durgical.com/en/histology/from-biopsy-to-slide-fixation-sectioning-frozen-section/)
- [Cilia, microvilli and stereocilia](https://durgical.com/en/histology/cilia-microvilli-and-stereocilia/)
- [Glomerulus and the filtration barrier: podocytes, mesangium, JGA](https://durgical.com/en/histology/glomerulus-and-the-filtration-barrier-podocytes-mesangium-jga/)
- [Organelles: nucleus, ER, Golgi, mitochondria, lysosomes, peroxisomes](https://durgical.com/en/histology/organelles-nucleus-er-golgi-mitochondria-lysosomes-peroxisomes/)

## Related conditions

- [Bronchiectasis](https://durgical.com/en/conditions/bronchiectasis/)

[← All of histology](https://durgical.com/en/histology/)

Educational content on normal microscopic structure and its clinical relevance; no substitute for studying slides or for a health professional's advice.

Sources: [Tissue preparation 9](https://digitalhistology.org/histology-basics/tissue-preparation/tissue-9/) (Digital Histology, 2024); [Stains 3](https://digitalhistology.org/histology-basics/stains/stains-3-2/) (Digital Histology, 2024); [Tissue preparation 1](https://digitalhistology.org/histology-basics/tissue-preparation/tissue-1/) (Digital Histology, 2024).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/histology/electron-microscopy-what-it-shows-that-light-can-t/