Atom

The atom was the basic unit of matter that made up everything in the universe. All atoms were held together by electrical charge.

The Bad Wolf entity was powerful enough, somehow, to destroy the Dalek Fleet attacking Earth in 200,100 by reducing every Dalek and every ship to atoms. (TV: The Parting of the Ways)

Davros had developed and successfully tested a weapon, the reality bomb, capable of cancelling the electric charge that held atoms together. (TV: Journey's End)


 * The fact that the reality bomb would have destroyed every universe if dentonated in the Medusa Cascade might mean that, despite different laws of physics, all of reality is composed of atoms.