  The life of disk galaxies is likely punctuated with the birth (spontaneous or
induced), the aging (quick or slow), and the death (sudden or progressive) of
bars. These events are responsible for various major changes of the galaxy
which occur both on dynamical ($\sim$0.1 Gyr) and cosmological ($\sim$10 Gyr)
time-scales, as well as both on large- ($\ga$10 kpc) and small-scales ($\la$1
kpc). These modifications affect the morphology, the orbital structure, the
dynamics, the star formation and central fueling rates, the abundance profiles,
etc. As a consequence, remarkable galaxy metamorphoses within the Hubble
sequence can be observed. The formation and the fate of gaseous bars are also
briefly examined.
