'Micro-units' and 'Macro-units'... What should we concern ourselves with?.. and,

I'll try and explain...

What I mean by 'micro-units' would be the most indivisible units that exist, like 'quarks' or something similar... and what I mean by 'macro-units' would be the most complex units that exist, like a complex chemical compound, or complex body (like the human body) or something very, very great like the Universe...

We have all had these thoughts...
'What is the smallest part of the Universe?', and
'What are the bounds of the Universe? (including what's outside the Universe)

We tend to go from the smallest perceptible thing to the largest thing... Not so much in between...

What this post would be about is, what are they really, from the smallest part to the largest whole...

What should we concern ourselves with to get bearing in this area? What use could it have?

I guess it centres around the physical system you're thinking about... your bearings would centre around that... Such that, if you're thinking, say about eating, you would think primarily about the digestive system, the food sources, and anything directly related to you getting some food and eating it... The bearing here would be those things related to you eating something...

What kinds of things should we concern ourselves with, what systems will we be using, how small and large can we get to and what lies in between?

I hope this made some kind of sense, and look forward to hearing your thoughts on the topic...