Dark matter represents one of the principal ingredients of the standard model, and its existence is demonstrated by a great number of astronomical observations. Amongst these we recall the rotation curves of spiral galaxies and the masses of galaxy clusters, along with the already mentioned fluctuations of the cosmic microwave background and the large scale distribution of galaxies. It appears clear from these observations that besides a small fraction of "unilluminated" conventional matter, 90% of dark matter must be in the form of massive elementary particles that interact with eachother (and ordinary matter) only via the force of gravity. What these particles might be remains one of the great mysteries of the cosmological model, strictly correlated with problems of fundamental physics and so to the research of the infinitely small. Research aimed at identifying the dark matter particles are both direct and indirect in nature, depending on whether they make use of an interaction with the atoms of a detector, or rely on the secondary particles expected as the result of particle annihilation. This research is mainly the prerogative of particle physics, with complimentary information provided by astronomical observations in the X-ray, optical and millimetric bands.

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