I received a follow up question from the high school student, wondering why scientists can't look at subatomic particles. Why can't they just X-Ray them or something.
The answer is really kind of fun, so I thought I'd share it here as well.
PART I:
"Inside the World's Most Powerful New Microscopes"
PART II: http://www.bbc.com/earth/story/20151120-how-do-we-know-that-things-are-really-made-of-atoms
"How do we know that things are really made of atoms?"
PART III: "The small size of subatomic particles is perhaps most convincingly expressed not by stating their absolute units of measure but by comparing them with the complex particles of which they are a part. An atom, for instance, is typically 10−10 metre across, yet almost all of the size of the atom is unoccupied “empty” space available to the point-charge electrons surrounding the nucleus. The distance across an atomic nucleus of average size is roughly 10−14 metre—only 1/10,000 the diameter of the atom. The nucleus, in turn, is made up of positively charged protons and electrically neutral neutrons, collectively referred to as nucleons, and a single nucleon has a diameter of about 10−15 metre—that is, about 1/10 that of the nucleus and 1/100,000 that of the atom. (The distance across the nucleon, 10−15 metre, is known as a fermi, in honour of the Italian-born physicist Enrico Fermi, who did much experimental and theoretical work on the nature of the nucleus and its contents.)" From the Encyclopedia Britannica, https://www.britannica.com/science/subatomic-particle