  Comparison of the ISM properties of a wide range of metal-poor galaxies with
normal metal-rich galaxies reveals striking differences. We find that the
combination of the low dust abundance and the active star formation results in
a very porous ISM filled with hard photons, heating the dust in dwarf galaxies
to overall higher temperatures than their metal-rich counterparts. This results
in photodissociation of molecular clouds to greater depths, leaving relatively
large PDR envelopes and difficult-to-detect CO cores. From detailed modeling of
the low-metallicity ISM, we find significant fractions of CO-dark H2 - a
reservoir of molecular gas not traced by CO, but present in the [CII] and
[CI]-emitting envelopes. Self-consistent analyses of the neutral and ionized
gas diagnostics along with the dust SED is the necessary way forward in
uncovering the multiphase structure of galaxies
