microscopy

Microscopy is the science of using microscopes to observe objects that are too small to be seen with the unaided eye. It encompasses optical (light) microscopy, electron microscopy, and scanning probe techniques, and it plays a central role in biology, medicine, and materials science. The development of microscopy spans from early lens-based devices in the 16th and 17th centuries to modern, highly specialized instruments. Notable milestones include the refinement of compound microscopes, Anton van Leeuwenhoek’s observations of microorganisms, Robert Hooke’s descriptions in Micrographia, and Ernst Ruska’s creation of the first practical electron microscope in the 1930s.

Optical microscopy uses light and lenses to magnify specimens. Resolution—the smallest resolvable detail—is limited by wavelength and numerical aperture, and in practice is around 200 nanometers for standard bright-field illumination. Various imaging modes increase contrast, including phase-contrast, differential interference contrast (DIC), and dark-field. Fluorescence microscopy employs fluorescent labels to visualize specific structures or molecules, providing high specificity and enabling multi-channel imaging. Wide-field, confocal, and super-resolution methods (such as STED, PALM, and STORM) push the boundaries of resolution beyond classical limits.

Electron microscopy and scanning probe techniques broaden the reach of microscopy. Transmission electron microscopy (TEM) uses electron beams to reveal internal structure at sub-nanometer resolution, often requiring thin sections and vacuum. Scanning electron microscopy (SEM) images surfaces with great depth of field. Scanning probe methods, including atomic force microscopy (AFM) and scanning tunneling microscopy (STM), map surfaces at atomic or near-atomic resolution and can operate in air or liquid.

Applications span life sciences, pathology, materials science, and nanotechnology. Advances such as cryo-electron microscopy, correlative light and electron microscopy (CLEM), and improved sample preparation continue to expand capabilities while addressing artifacts and practical constraints.