  While low-z Type Ia supernovae are used to measure the present rate of
expansion of the Universe, high-z Type Ia measure its variation due to the
cosmic matter-energy content. Results from those determinations imply a low
matter density Universe with a non-zero cosmological constant (vacuum-energy
component). The expansion rate of the Universe accelerates, according to these
determinations. The validity of the Type Ia supernova approach for this
cosmological research is addressed. An account is given of additional prospects
to further investigate through supernovae what the Universe is made of. Those
attempts range from constraining the large scale dark matter distribution to
further test and interpret the presence of a vacuum energy component.
