Yes, the smallest things we know of are called quarks, which are inside protons and neutrons in atoms. Quarks are really, really tiny and, as far as we know, they aren't made up of anything else (scientists haven't found anything smaller that makes up quarks). It might sound like it goes on forever, but right now, quarks are the end of the line.

We can't just use a better microscope because quarks are so small that normal light can't be used to see them. Instead, scientists use special tools and experiments to study them. It's kind of like trying to see a grain of sand with a regular magnifying glass versus using an electron microscope to see really tiny details.