In terms of population the most extreme example is the Pitcairn Islands, with ca. 47 inhabitants. It is considered a separate country, though a dependent area of the United Kingdom.
The term microstate is sometimes used as a synonym for micronation. The distinction is that micronations are not generally recognised as sovereign states except by other micronations.
See also: List of countries by population and List of countries by area.
Microstate is also used in thermodynamics to refer to a specific configuration of particles of a material in contrast to macrostate[?] which describes the bulk properties (i.e. the temperature and pressure) of that material.
wikipedia.org dumped 2003-03-17 with terodump