Three forces act in the micro cosmos. They act directly between quarks and leptons at this level. Since the word "force" sometimes gives a misleading picture, one instead uses the word "interaction". The Standard Model describes the different interactions with the help of force carrying particles. The three types of interaction are:

• the strong interaction (acts on quarks; mediated by gluons)
• the weak interaction (acts on both quarks and leptons; mediated by vector bosons)
• the electromagnetic interaction (acts on charged particles; mediated by photons)

There is a fourth type of interaction that is not a part of the Standard Model: gravity. It is supposed to be mediated by the graviton (not yet discovered). The gravity between single particles is so weak that it is negligible in micro cosmos.