  The evolution of white dwarfs is a simple gravothermal process. This means
that their luminosity function, i.e. the number of white dwarfs per unit
bolometric magnitude and unit volume as a function of bolometric magnitude, is
a monotonically increasing function that decreases abruptly as a consequence of
the finite age of the Galaxy. The precision and the accuracy of the white dwarf
luminosity functions obtained with the recent large surveys together with the
improved quality of the theoretical models of evolution of white dwarfs allow
to feed the hope that in a near future it will be possible to reconstruct the
history of the different Galactic populations.
