  We discuss processes in galactic cosmic ray (GCR) acceleration sites -
supernova remnants, compact associations of young massive stars, and
superbubbles. Mechanisms of efficient conversion of the mechanical power of the
outflows driven by supernova shocks and fast stellar winds of young stars into
magnetic fields and relativistic particles are discussed. The high efficiency
of particle acceleration in the sources implies the importance of nonlinear
feedback effects in a symbiotic relationship where the magnetic turbulence
required to accelerate the CRs is created by the accelerated CRs themselves.
Non-thermal emission produced by relativistic particles (both those confined in
and those that escape from the cosmic accelerators) can be used to constrain
the basic physical models of the GCR sources. High resolution X-ray synchrotron
imaging, combined with GeV-TeV gamma ray spectra, is a powerful tool to probe
the maximum energies of accelerated particles. Future MeV regime spectroscopy
will provide unique information on the composition of accelerated particles.
