Elementary particles --

There are many situations which do not fall under the classical limit and for which quantum mechanics becomes quite important. Usually these situations involve the smallest possible objects, elementary particles, things like electrons, photons and quarks. Often people get hung up on whether these elementary particles are really ``particles'' or ``waves.'' But, particle and wave are concepts of classical physics, which has very little to do with such objects. Indeed, some things which elementary particles do may remind us of our classical concepts of particle or wave behavior, but we should always keep in mind that elementary particles are elementary particles, neither waves nor particles. The task of quantum mechanics is to observe and determine what these objects do and then to learn how to describe this behavior without bringing in our own prejudices. When we do this, we see that it turns out that the elementary particles have much more in common with each other than they do with our concepts of particles and waves.