A medical physicist is a professional who applies the principles and methods of both physics and medicine. They focus on the areas of prevention, diagnosis, and treatment, as well as ensuring quality services and prevention of risks to the patients, and members of the public in general. A medical physicist plays a fundamental role in applying physics to medicine, but particularly in the diagnosis and treatment of cancer. The scientific and technological progress in medical physics has led to a variety of skills that must be integrated into the role of a medical physicist in order for them to perform their job. The "medical services" provided to patients undergoing diagnostic and therapeutic treatments must, therefore, be the result of different but complementary skills.