There are lots of them. Perhaps you mean neutrinos?
Individual atoms and molecules also exist in outer space, as a kind of very thin gas. Space is not a perfect vacuum. There are also sub-atomic particles, such as cosmic rays, in space.
A grain
An electron is a tiny particle that carries a negative electrical charge. It is a fundamental subatomic particle found in atoms.
Light comes in tiny distinct packages called photons.
A tiny particle or packet of light is called a photon. These particles are the basic unit of light and carry electromagnetic radiation.
So far, the "quark" is believed to be the most tiny fundamental particle.
Particle in the English language refers to the a very tiny piece of something.
ATOM
The smallest particle of matter having distinctive chemical and physiacl properties; a tiny particle
The particle theory is called the "particle model" or "particle theory of matter." It proposes that all matter is composed of tiny particles that are in constant motion.
That will vary from particle to particle.
photon