"Within each density there are seven sub-densities"

[Lavazza]

As a side effect, exploring ever smaller particles is to a certain extent pointless. Because there is no "Smallest" particle. You can't get to the bottom of it. However, it is useful to understand the interaction between larger and smaller particles to get an insight in the bigger picture.

Actually from what I've read on the subject (and because I cannot resist a debate ), we cannot conclude that there is no smallest particle because we have not yet been able to devise a means of seeing anything smaller than certain scales.

The math behind String Theory for example poses that there are elements of the physical universe (strings) that are so incredibly tiny that we may never directly observe them. Which of course is why it may always be a theory only, unless we are able to collect evidence of their existence by other means. Check this out:

A Sense of Scale
The strings of string theory are unimaginably small. And when we say "unimaginably," we mean it: Your average string, if it exists, is about 10-33 centimeters long. That's a point followed by 32 zeros and then a 1. It's a millionth of a billionth of a billionth of a billionth of a centimeter. (Physicists stick to metric.) Or think of it this way: if an atom were magnified to the size of the solar system, a string would be the size of a tree. Yup, real small.

I might also present Zeno's paradox for your consideration (http://en.wikipedia.org/wiki/Zeno%27s_paradoxes) In short Zeno suggests that motion is impossible because to move anywhere requires us to reach the mid-way point of that destination first. But if there is no smallest particle (or unit of space) then there would be an infinity of half-way points to reach first. Yet it is a paradox to say so because regardless of this, we reach our destinations when we wish to travel somewhere. SO I might say that since we can go places, a smallest unit must exist.

Sorry to derail the thread so heavily with these ramblings. I've had my morning coffee and my brain is jumping around in my skull.