CSN2 coordinates research in the field of astroparticle physics. Its main purpose is to test the idea that all the fundamental interactions between the constituents of matter are unified in one fundamental force (the Grand Unified theory) and conduct research into new types of components of matter and energy (dark matter, dark energy). Since the only direct way of testing these theories would be to create much higher energy levels in a laboratory than the levels achievable using particle accelerators, they are tested indirectly using the universe as a natural accelerator. Astroparticle physics experiments are performed to study cosmic background radiation, cosmic rays, neutrinos, gravitational waves, very-high-energy gamma rays, other rare particles that could provide important clues to explain the matter-antimatter asymmetry in the universe, and particles that are thought to constitute the dark matter. The study of gravity and particularly of the gravitational waves predicted by Einstein, the existence of which has never directly been observed, represents one of the most fascinating challenges for scientists today.