The microscopic scale (from Ancient Greek μικρός (mikrós) 'small' and σκοπέω (skopéō) 'to look (at); examine, inspect') is the scale of objects and events smaller than those that can easily be seen by the naked eye, requiring a lens or microscope to see them clearly.[1] In physics, the microscopic scale is sometimes regarded as the scale between the macroscopic scale and the quantum scale.[2][3] Microscopic units and measurements are used to classify and describe very small objects. One common microscopic length scale unit is the micrometre (also called a micron) (symbol: μm), which is one millionth of a metre.
We shall call a system 'microscopic' (i.e., 'small scale') if it is roughly of atomic dimensions or smaller (say of the order of 10 Å or less).