Type Ia supernovae are powerful probes of dark energy. In the
first part of this proceeding, we briefly review the status of
supernova cosmology presenting the importance of understanding
systematics associated to this probe. In a second part, we focus on
an important issue in curent Supernova analysis: the influence of
the SN host environments in measurement of cosmological distance with
Type Ia supernovae and their consequences on derivation of
cosmological parameters.