  One of the great scientific enigmas still unsolved, the existence of dark
matter, is reviewed. Simple gravitational arguments imply that most of the mass
in the Universe, at least 90%, is some (unknown) non-luminous matter. Some
particle candidates for dark matter are discussed with particular emphasis on
the neutralino, a particle predicted by the supersymmetric extension of the
Standard Model of particle physics. Experiments searching for these relic
particles, carried out by many groups around the world, are also discussed.
These experiments are becoming more sensitive every year and in fact one of the
collaborations claims that the first direct evidence for dark matter has
already been observed.
