The study of high-energy cosmic rays (CRs) is a multifaceted field that addresses questions ranging from shock acceleration in astrophysical objects to the nature of dark matter and beyond the Standard Model particle physics. The discovery of CRs by Victor Hess in 1911 marked the beginning of a century-long exploration, leading to significant advancements in particle physics, such as the discovery of the positron, muons, and pions. Nuclear and particle physics have also contributed to the understanding of CR propagation and interactions, with data from accelerators playing a crucial role in modeling extensive air showers (EAS). The CR energy spectrum, which extends from below 1 GeV to above \(10^{20}\) eV, is characterized by a "knee" at around \(10^{15}\) eV and an "ankle" at \(5 \times 10^{18}\) eV, indicating a transition from galactic to extra-galactic sources. The knee remains a mystery, with possible explanations including the maximum energy of galactic accelerators and the formation of quark-gluon plasma. The search for dark matter and antimatter through CR measurements, such as antiprotons and antimuclei, is another key area of interest. High-energy CRs, particularly those above \(10^{20}\) eV, are believed to originate from distant sources like active galactic nuclei, but their exact nature and origin remain largely unknown. The Pierre Auger Observatory and other large experiments are expected to provide crucial data to resolve these questions, making CR physics a central pillar of Particle-Astrophysics.The study of high-energy cosmic rays (CRs) is a multifaceted field that addresses questions ranging from shock acceleration in astrophysical objects to the nature of dark matter and beyond the Standard Model particle physics. The discovery of CRs by Victor Hess in 1911 marked the beginning of a century-long exploration, leading to significant advancements in particle physics, such as the discovery of the positron, muons, and pions. Nuclear and particle physics have also contributed to the understanding of CR propagation and interactions, with data from accelerators playing a crucial role in modeling extensive air showers (EAS). The CR energy spectrum, which extends from below 1 GeV to above \(10^{20}\) eV, is characterized by a "knee" at around \(10^{15}\) eV and an "ankle" at \(5 \times 10^{18}\) eV, indicating a transition from galactic to extra-galactic sources. The knee remains a mystery, with possible explanations including the maximum energy of galactic accelerators and the formation of quark-gluon plasma. The search for dark matter and antimatter through CR measurements, such as antiprotons and antimuclei, is another key area of interest. High-energy CRs, particularly those above \(10^{20}\) eV, are believed to originate from distant sources like active galactic nuclei, but their exact nature and origin remain largely unknown. The Pierre Auger Observatory and other large experiments are expected to provide crucial data to resolve these questions, making CR physics a central pillar of Particle-Astrophysics.