Like, foam foam? Or.. Styrofoam? No and no. Quantum foam. It's safe to say empty space is- empty. Right? Wrong. The universe can't tolerate that which is why particles are constantly popping into and out of existence all over the place. They’re called virtual particles, but they are proven to be very real. The catch is that they exist for only a fraction of a second, which is long enough to break some fundamental laws of physics but quick enough that this doesn’t actually matter. For instance, say you stole something from a store, but put it back on the shelf half a second later. You broke a rule but, in the end it doesn't effect anything. Reminding them of the shifting bubbles in the head of a soft drink, scientists have respectively named this phenomenon ‘quantum foam.'