What is dust made of ?

This question should be presented to police investigators who are able to find all sorts of clues in dust.  Dust in a room may contain skin scaling of people who were there, tiny pieces of fabric, tiny grains of sand, crumbs of dried food particles. In short, dust contains all sorts of light substancess that are easily carried by air currents.

As Rock indicates, dust is surprisingly complicated.

There are different kinds of dust: space dust; dust in a desert; dust inside a home; etc.  House dust includes skin cells (from people and possibly pets), fibers (from bedding, clothes, etc.), and other particles created inside the house, as well as outside (soil, pollutants, etc.).

A short description of dust appears on WiseGeek.  An entire book on dust (The Secret Life of Dust) is available at Amazon.

yes dust is made up up of dead skin cells but i can see where rock is coming from although it is difficult to trace the dna is skin cells that are dead, and even if it was possible it would give false suspects because a simple handshake or hug rubs off skin cells to another person also touching everday items in a public area like a shopping cart for example. the point is for police or crime scene investigators to use dust as a form of tracing who has been un a certain place would give too broad of a spectrum of possible suspects

What does Ashes to Ashes  mean?