What aspect of art was explored in detail by the pointillist painters?

Answer 1

Light. A scientific aproach so to speak.

They tried to make colors mix in the eye by placing them together and letting the viewers eye mix it to a color they intended them to see. That way colors would remain more vibrant and clear.... that was the idea.

It took untill the invention of color pictures to actually get it right and not see the dots at all.

Answer 2

Take a lens and look at a piece of colour printing. That will show you the way a pointillist painter aimed to produce a vibrant colour/light effect. Unfortunately it took so long to do that the results are often stiff and boring. See Seurat's figures.