  In classical mechanics matter and fields are completely separated. Matter
interacts with fields. For particle physicists this is not the case. Both
matter and fields are represented by particles. Fundamental interactions are
mediated by particles exchanged between matter particles. In this paper we
explain why particle physicists believe in such a picture, introducing the
technique of Feynman diagrams starting from very basic and popular analogies
with classical mechanics, making the physics of elementary particles
comprehensible even to high school students, the only prerequisite being the
knowledge of the conservation of mechanical energy.
