Years ago, the ancients thought that the world was made of five basic elements: Earth, Air, Fire, Water, and Dust. They believed that these five things made up everything we could see (and also the stuff we couldn't).
Take the example of a stick. If they burned it they saw a flame (so the stick had Fire in) and also ash (so there was Earth in there) and some smoke (Air). If they left the stick lying around for long periods without letting their wives dust it it generated dust (so it had Dust in too).
This theory was all very well and good for an ancient society, but in the modern world it was quickly realised that the theory didn't cut it. The main question was: 'If Dust is just one of the elements, why does every object in the known world generate the stuff?' (The word "Dust", incidentally, comes from the word "Duster" or "collector of Dust".) It was quickly realised that under special dank attic conditions, even Water (previously thought to be a separate element) could be made to generate Dust.
The new theory came along in 1800, when it was realised that only Dust is in fact an element, and it alone makes up everything else. The Bible helped with this revelation, with its assertions that people are made of dust and will eventually return to dust. This is believed to be what God really meant all along.
New discoveries were made thick and fast after this, and a team of scientists working in the loft of a deserted mansion were the first to find out that it comes in six distinct types or "Flavours":
Dust That Gets Up Your Nose And Makes You Sneeze
The last one was dismissed as rather unimportant since it was thought to be boring, especially compared to type 5 which interested Pharmacists greatly for the next hundred years or so.
Only recently have the pedants of this world started to point out that Dust is in fact made of smaller particles which they call "atoms", but when asked to prove that this is true they will start using very sciency words and so are Not To Be Trusted. Dust is truly the Smallest and Most Annoying particle in the universe, and anyone who says otherwise is just being Boring.