Acceleration of galactic cosmic rays

More than a century ago it was discovered that the Earth is bombarded by a penetrating radiation of cosmic origin, whose flux was later found to be dominated by charged particles. The discovery of cosmic rays led to many questions about their origin and about the way that they reach us from large distances. Here I will summarize some recent developments in our understanding of the acceleration mechanisms that energize a small number of thermal particles to highly non-thermal energies, with special attention on diffusive acceleration at supernova remnant shocks.