The study of the phase structure
of strongly interacting matter under extreme conditions of
temperature and density addresses fundamental aspects of QCD, among
them the mechanism of confinement, the origin of the spontaneous
breaking of chiral symmetry and their importance for the generation
of mass. Dileptons emitted in collisions of heavy ions offer the
unique opportunity to investigate the microscopic properties of
strongly interacting matter under such extreme conditions. This
contribution discusses important experimental results in dilepton
spectroscopy obtained so far by HADES. I will also address the
long-term goal of this research at GSI/FAIR, i.e., the establishment
of a complete excitation function of dilepton production from
energies of $1A \mathrm{GeV}$ up to $11 A \mathrm{GeV}$ with HADES
and CBM.
Nuclear
Physics Colloquium