During the 19th and 20th centuries, physicists began to probe deep into the nature of matter and energy. In so doing, they quickly realized that the rules which govern them become increasingly blurry the deeper one goes. Whereas the predominant theory used to be that all matter was made up of indivisible atoms, scientists began to realize that atoms are themselves composed of even smaller particles.
It is often claimed that the Ancient Greeks were the first to identify objects that have no size, yet are able to build up the world around us through their interactions. And as we are able to observe the world in tinier and tinier detail through microscopes of increasing power, it is natural to wonder what these objects are made of.