The use of charged particles and nuclei in cancer therapy (hadrontherapy) is one of the most successful cases of application of nuclear physics to medicine. The physical advantages in terms of precision and selectivity, combined with the biological properties of densely ionizing radiation, make the charged particle approach an elective choice in a number of cases. Hadrontherapy is in continuous development and it is an interdisciplinary field where physicians, biologists and physicists contribute together. After a brief review of the status and development of Charged Particle Therapy, the main focus of this seminar is to discuss those aspects where nuclear and particle physicists are presently active. Indeed the role of physicists is still very important for the progress of Particle Therapy. Beyond many crucial technological aspects, like the design of new compact and cheaper accelerators, impulse is given to algorithms and software, investigation of the relevant properties of nuclear interactions and the development of dedicated detectors. One of the most important aspects where the contribution of physicist is important concerns the uncertainties on particle range, which is a problem closely connected with the ability to achieve the promised precision in therapy. At present, uncertainties in particle range lead to the employment of safety margins, at the expenses of treatment quality. One of the research items in particle therapy is therefore aimed at developing methods to verify the particle range in patients in real time. Non-invasive “in-vivo” monitoring of the particle range can be performed by detecting secondary radiation, emitted from the patient as a result of nuclear interactions of charged hadrons with tissue, including β+ emitters, prompt photons, and charged particles. Dedicated detector systems are being developed. The proposed approaches require reliable and precise Monte Carlo predictions and a dedicated research activity for the continuous improvement of existing models is also necessary.