microscopic

Microscopic describes objects or phenomena that cannot be seen with the naked eye because they are smaller than the limit of human vision. The threshold is relative to the observer and observing conditions, but in everyday use it refers to objects typically smaller than about 0.1 millimeters. The term is contrasted with macroscopic, which denotes things large enough to be seen unaided. The concept underpins microscopy, the practice of using instruments to magnify and resolve fine detail.

Microscopy employs various techniques. Optical or light microscopy uses visible light and lenses to magnify specimens, with staining and contrast methods to enhance features. Electron microscopy uses beams of electrons for far higher resolution, including scanning electron microscopy (SEM) for surfaces and transmission electron microscopy (TEM) for internal structure. Fluorescence, confocal, and super-resolution methods extend capabilities of light microscopes. Scanning probe techniques such as atomic force microscopy (AFM) and scanning tunneling microscopy (STM) operate at the nanoscale. Sample preparation, fixation, and staining are common steps to preserve structure and improve contrast. Resolution is fundamentally limited by wavelength in optical methods, whereas electron and scanning probe methods reach nanometer to sub-nanometer scales.

Objects commonly described as microscopic include cells, bacteria, and many protozoa, as well as pollen grains, crystals, fibers, and nanoparticles. Microbiology, materials science, and geology all rely on microscopic analysis to observe morphology, structure, and composition. The term also appears in broader contexts to indicate careful, detailed examination of small-scale features in a wide range of disciplines.