The domain of validity of standard thermodynamics and Boltzmann-Gibbs stati
stical mechanics is discussed and then formally enlarged in order to hopefu
lly cover a, variety of anomalous systems. The generalization concerns none
xtensive systems, where nonextensivity it; understood in the thermodynamica
l sense. This generalization was first proposed in 1988 inspired by the pro
babilistic description of multifractal geometries, and has been intensively
studied during this decade. In the present effort, after introducing some
historical background, we briefly describe the formalism, and then exhibit
the present status in what concerns theoretical, experimental and computati
onal evidences and connections, as well as some perspectives for the future
. In addition to these, here and there we point out various (possibly) rele
vant questions, whose answer would certainly clarify our current understand
ing of the foundations of statistical mechanics and its thermodynamical imp
lications.