There are no particles in the same sense as in the standard model where particles have a discrete something at their center analogous to a grain of sand. However, there are electrons, protons and neutrons. These are made up of concentric spherical waves. An in-wave moves inward toward the center, undergoes spherical rotation and then moves outward from the center as an out-wave. Combined, their amplitudes add up to a spherical standing wave. It is impossible to say where the electron starts and ends since it is made up of only these waves and these waves potentially propagate endlessly. Also, a portion of the out-wave of one electron is a portion of the in-wave of another electron, so even the boundary between electrons is hard to define.

As the animation on the right illustrates, an in-wave is really a collection of separate spherical waves coming from many different particles. At one common edge, all these in-waves form a single wavefront that is the in-wave. In the animation it's where all the waves meet to form a dark, collapsing ring. This is called Huygens principle (or more precisely, the Huygens-Fresnel principle.) The red, blue and green waves in the animation are so colored to help show that the animation is made up of many separate circular waves.

So only a small portion of the out-wave of one particle arrives at a second particle as part of that second particle's in-wave. That small part will then be rotated 720 degrees, and returned to the original particle as part of a new, expanding out-wave.