Quantum Field Theory
The quantum field theory stems from the alliance of quantum mechanics and special relativity. In this framework particles are elementary excitations of a more fundamental object: a field, that takes on different values at various points in spacetime. For the water on an ocean, elementary excitations are waves propagating on the surface. In quantum mechanics, the height of the waves can take only certain precise values (they are "quantised") and these "elementary waves" are particles.