  In recent years, exciting developments have taken place in the identification
of the role of cosmic rays in star-forming environments. Observations from
radio to infrared wavelengths and theoretical modelling have shown that
low-energy cosmic rays (<1 TeV) play a fundamental role in shaping the chemical
richness of the interstellar medium, determining the dynamical evolution of
molecular clouds. In this review we summarise in a coherent picture the main
results obtained by observations and by theoretical models of propagation and
generation of cosmic rays, from the smallest scales of protostars and
circumstellar discs, to young stellar clusters, up to Galactic and
extragalactic scales. We also discuss the new fields that will be explored in
the near future thanks to new generation instruments, such as: CTA, for the
$\gamma$-ray emission from high-mass protostars; SKA and precursors, for the
synchrotron emission at different scales; and ELT/HIRES, JWST, and ARIEL, for
the impact of cosmic rays on exoplanetary atmospheres and habitability.
