The dark matter problem is almost a century old. Since the 1930s evidence has been growing that our cosmos is dominated by a new form of non-baryonic matter that holds galaxies and clusters together and influences cosmic structures up to the largest observed scales. At the microscopic level, we still do not know the composition of this dark, or invisible, matter, which does not interact directly with light. The simplest assumption is that it is made of new particles that interact with gravity and, at most, weakly with known elementary particles. I will discuss searches for such new particles, both space- and Earth-bound, including those experiments placed in deep underground laboratories. While a dark matter particle has not yet been identified, even after decades of concerted efforts, new technological developments and experiments have reached sensitivities where a discovery might be imminent, albeit certainly not guaranteed.