Micropatrology (from Greek "micro" small, and Latin "patria" country) is "the study of small and little-known nations and territories."
Generally it deals with countries (and efforts to create new countries) smaller than Luxembourg.
The field has existed informally since the 1880's as a hobby subject, notably in the works of the Duc d'Astraudo. The term was coined in 1973 by Frederick W. Lehmann, president of the International Micropatrological Society.
See Micronation for details about specific countries. Micropatrology deals with countries that have a real physical existence in the world, or that plan to achieve it, and not with fantasy-states, cyber-nations, or fictional utopias.