- instrument for observing objects too small for the unaided eye
- optical (light) microscope: magnification up to ~1500x, resolves to ~200 nm
- electron microscope: transmission (TEM) and scanning (SEM), resolves to atomic scale
- scanning probe: atomic force microscope (AFM), scanning tunneling microscope (STM)
- fluorescence microscopy: labels specific molecules in living cells
- revealed the cellular basis of life, bacteria, viruses, species microstructure
- enabled semiconductor fabrication inspection and quality control
- cryo-electron microscopy resolves protein structures without crystallization
- complementary to telescope: one reaches inward, the other outward
- essential for biology, materials science, and nanotechnology