Last year observations had a profound impact on our views on the amount and
nature of dark matter in the universe. We give a brief review of the recent
history of dark matter models beyond the pure cold dark matter universe. In
view of the most recent cosmological data, we then go on to discuss models with
a positive cosmological constant. Finally we explicitly analyse a class of
particle physics models for a dynamical cosmological component with negative
pressure (``quintessence''), in the context of supersymmetric theories.Comment: 13 pages; Talk given by Antonio Masiero at the 8^th International
Workshop on Neutrino Telescopes, 23-26 Feb. 1999, Venice, Italy. To be
published in the Proceeding
