  The dust in galaxies makes radiation transport calculations in them
absolutely necessary. It is not only common practice in Astrophysics, but also
wisdom, to try to make as simple models as possible to simulate physical
systems. For spiral galaxies, however, this turned out to be catastrophic. For
years, the major question of the opacity of spiral galaxies kept the community
divided, because the models were too simple. A spiral galaxy appears, to first
order, to have exponential distributions of stars and dust, which cannot be
approximated with uniform distributions. We will review the radiative transfer
methods used in galaxies and we will comment on their pluses and minuses. We
will also present some of the main results of the application of one of the
methods to the observations.
