Despite the enormous efforts done in very recent years, both theoretically and experimentally, thebasic three questions about the CR origin remain without clear answers: what are their sources,how are they accelerated, how do they propagate? Gamma-ray astronomy plays a fundamentalrole in this field. Both relativistic protons and electrons can emit in the gamma-ray band withdifferent processes but only the detection of hadronic gamma-ray emission is a direct proof ofCosmic-Ray acceleration. Distinguishing leptonic and hadronic components is one of the mosttricky issues in the high energy astrophysics, however, a gamma-ray detection at about 100 TeVwould be a direct proof of the hadronic origin of the emission. Consequently, not only it woulddirectly confirm the presence of CR acceleration in a source but also it gives us a large amountof information about their sources, their parent protons and their propagation.The ASTRI Mini-Array, with its unprecedented sensitivity and angular resolution at E>10 TeV, will provide afundamental contribution to close some of the most important CR open issues.