High energy particles from outer space were discovered more than one hundred years ago. The studies of cosmic rays have resulted in many discoveries in particle physics, such as the discoveries of the positron, the muon, and the pion, that led to the development of the accelerator-based particle physics. Today the focus of astroparticle physics research has turned to using these particles as messengers to study the universe: How and where these particles are produced and accelerated? How they interact and propagate before reaching the Earth? What is the particle composition at different energies? Can the still elusive Dark Matter produce the high energy anomalies that have been observed in cosmic rays? A century after the discovery of cosmic rays, we are still a long way from answering these fundamental questions, because of the daunting challenge to disentangle many unknown initial and boundary conditions with only particles that reached the Earth. However, important progresses have been made with the complementary approaches of using large ground-based experiments, such as AUGER, IceCube, HESS, and space-borne missions, such as PAMELA, Fermi, AMS, and DAMPE.