  In this chapter, a statistical measure of complexity and the Fisher-Shannon
information product are introduced and their properties are discussed. These
measures are based on the interplay between the Shannon information, or a
function of it, and the separation of the set of accessible states to a system
from the equiprobability distribution, i.e. the disequilibrium or the Fisher
information, respectively. Different applications in discrete and continuous
systems are shown. Some of them are concerned with quantum systems, from
prototypical systems such as the H-atom, the harmonic oscillator and the square
well to other ones such as He-like ions, Hooke's atoms or just the periodic
table. In all of them, these statistical indicators show an interesting
behavior able to discern and highlight some conformational properties of those
systems.
