  The nature of the dark matter in the Universe is one of the hardest unsolved
problems in modern physics. Indeed, on one hand, the overwhelming indirect
evidence from astrophysics seems to leave no doubt about its existence; on the
other hand, direct search experiments, especially those conducted with low
background detectors in underground laboratories all over the world seem to
deliver only null results, with a few debated exceptions. Furthermore, the lack
of predicted candidates at the LHC energy scale has made this dichotomy even
more puzzling. We will recall the most important phases of this novel branch of
experimental astro-particle physics, analyzing the interconnections among the
main projects involved in this challenging quest, and we will draw conclusions
slightly different from how the problem is commonly understood.
