The term 'small bit of matter' can be broken down into two crossword solutions: ATOM (4 letters) and PARTICLE (8 letters). An ATOM is the smallest unit of matter that still retains its chemical properties. It consists of a nucleus, which contains protons and neutrons, and electrons that orbit around the nucleus. A PARTICLE is a very small piece of matter that is too small to be seen with the naked eye. Particles are made up of atoms and molecules, and they are the building blocks of all matter.