One of the reasons of the increasing knowledge about the inner structure of matter is the development of an established model, "The Standard Model." It describes all known processes in the world of particles. This is the first time in history that there exists such a complete description of the inner structure of matter and the forces that act therein.
The Standard Model is arranged in three families of particles. All matter seen
around us is constructed of the u and d quark and the electron; all belonging to the first
family (in green). In the early universe, all three families of particles were important,
but since then the particles of family two (in yellow) and three (in red) have decayed
into family one particles.
The Standard Model also describes three of the fundamental forces in nature. The weak
force acts on all particles; the electromagnetic force acts on charged leptons and quarks;
while the strong force only acts on quarks.