Cosmic-rays: an Unsolved Mystery at All Energies!

We consider the phenomenology of cosmic-rays (CRs) and stress the interest of jointly studying their properties over the whole energy spectrum. While UHECRs are known to raise important physical and astrophysical problems, we recall that low-energy CRs also remain poorly understood, and we indicate the possibly important role of superbubbles in accelerating CRs up to a few EeV. We also investigate the viability of holistic models, and show that a unique type of sources producing CRs with a spectrum in E could in principle account for all the CRs in the universe.