Cosmic rays and magnetic monopoles research. The gallery hosting the MACRO (Monopole Astrophysics and Cosmic Ray Observatory) experiment in the Gran Sasso Laboratory, Italy, the largest underground laboratory in the world. A technician is laying down copper strips on the roof of the structure hosting the detectors. Macro will look for magnetic monopoles, exotic particles never seen so far, and highly energetic muons produced by the interaction between cosmic rays and atoms in the upper atmosphere. The copper strips are used to extract the electric charge generated within the detectors by muons or magnetic monopoles.