Physicists research physical phenomena, devise hypotheses, conduct experiments and draw conclusions from experimental data to explain the world around us. Physicists can work in either applied or theoretical physics, based on their skill set and available career opportunities. Most careers in physics require graduate-level education, especially in theoretical physics. Physicists study the nature of all matter and energy, including structures, behavior, formation/generation and the interactions between the two. Physics can broadly be divided into theoretical physics and experimental physics. Theoretical physics involves developing models, or theories, which attempt to explain and predict how and why certain aspects of the world work and behave. Experimental physics involves testing these theories, determining their limits and using the results to amend or strengthen the theory as appropriate. All physicists will generally work in both of these areas to some degree. Physicists working at universities will also be required to spend time teaching students. An Applied Physicist may have a variety of duties, depending on his or her area of research. Among the major fields of applied research are environmental geophysics, gravitation, nuclear physics and physics education. Theoretical physicists are almost exclusively employed in academia, so duties include teaching in addition to conducting research. On a large scale, physicists are responsible for designing experiments, implementing them using the scientific method and drawing conclusions which will be beneficial to the advancement of science and industry. A physicist can also educate others in advanced, intermediate and basic physics.