  Accelerated particles are ubiquitous in the Cosmos and play a fundamental
role in many processes governing the evolution of the Universe at all scales,
from the sub-AU ones relevant for the formation and evolution of stars and
planets to the Mpc ones involved in Galaxy assembly. We reveal the presence of
energetic particles in many classes of astrophysical sources thanks to their
production of non-thermal radiation, and we detect them directly at Earth as
Cosmic Rays. In the last two decades both direct and indirect observations have
provided us a wealth of new, high quality data about Cosmic Rays and their
interactions both in sources and during propagation, in the Galaxy and in the
solar system. Some of the new data have confirmed existing theories about
particle acceleration and propagation and their interplay with the environment
in which they occur. Some others have brought about interesting surprises,
whose interpretation is not straightforward within the standard framework and
may require a change of paradigm in terms of our ideas about the origin of
cosmic rays of different species or in different energy ranges. In this
article, we will focus on Cosmic Rays of galactic origin, namely with energies
below a few PeV, where a steepening is observed in the spectrum of energetic
particles detected at the Earth. We review the recent observational findings
and the current status of the theory about the origin and propagation of
Galactic Cosmic Rays.
