Explore the different types of microscopes used in biology, such as light microscopes, electron microscopes, and fluorescence microscopes, and learn how to prepare samples for microscopic analysis.
Microscopy Techniques in Biology
An organized overview of the main optical and electron microscopy methods, their principles, advantages, limitations, and typical applications.
| Technique | Light vs. Electron | Resolution (approx.) | Sample Requirement | Typical Use |
|---|---|---|---|---|
| Bright‑field (BF) microscopy | Light | 200 nm | Fixed, stained, thin sections | General histology, routine diagnostics |
| Phase‑contrast (PC) microscopy | Light | 200 nm | Live or fixed, unstained | Observation of transparent cells (e.g., bacteria, organelles) |
| Differential interference contrast (DIC) | Light | 200 nm | Live or fixed, unstained | High‑contrast 3‑D‑like images of live cells |
| Fluorescence microscopy (wide‑field) | Light | 200 nm | Fluorophore‑labeled specimens | Localization of proteins, nucleic acids |
| Confocal laser scanning microscopy (CLSM) | Light | 200 nm (laterally) / 500 nm (axially) | Fluorophore‑labeled, often fixed or live | Optical sectioning, 3‑D reconstruction |
| Super‑resolution fluorescence (STED, PALM/STORM) | Light | 20–50 nm | Fluorophore‑labeled, often fixed | Nanoscale protein distribution |
| Two‑photon microscopy | Light (infrared) | ~300 nm | Live tissue, deep penetration | In‑vivo imaging of thick specimens |
| Light‑sheet fluorescence microscopy (LSFM) | Light | 200 nm | Live or cleared specimens | Fast volumetric imaging of embryos, organoids |
| Scanning electron microscopy (SEM) | Electron | 1–5 nm | Fixed, dehydrated, conductive coating | Surface topography, morphology |
| Transmission electron microscopy (TEM) | Electron | 0.1–1 nm | Ultra‑thin sections (≈70 nm), heavy‑metal staining | Internal ultrastructure, organelle architecture |
| Cryo‑EM (cryo‑TEM, cryo‑ET) | Electron | 3–5 nm (single‑particle) | Vitrified, unstained specimens | Near‑native structures of macromolecules, complexes |
| Scanning transmission EM (STEM) | Electron | 0.5–2 nm | Thin sections, often stained | Combined surface/internal detail |
| Atomic force microscopy (AFM) | Mechanical probe | 0.1–10 nm | Live or fixed, any substrate | Surface topography, mechanical properties |