核衰变产生的微粒或电磁波放射物的原子或分子由于核衰变放出的一束微粒或电磁波 A stream of particles or electromagnetic waves emitted by the atoms and molecules of a radioactive substance as a result of nuclear decay.
众所周知，世界是由叫做原子的小微粒组成的。 As is known to all, the world is made up of small particles called atoms.
物质是由叫做分子的微粒组成的。 Substances consist of small particles called molecules.