1. The "Standard Model" of particle physics describes the fundamental interactions (forces)
between elementary particles. It includes the theory of strong interactions (quantum
chromodynamics or QCD) and the unified theory of weak and electromagnetic
interactions (electroweak). Gravity is not included in the theory though it is shown in the
table below for completeness.
In the 'Standard Model' the mediators of the forces are called BOSONS.
The fundamental constituents of matter are named FERMIONS. All matter is built from
these particles.

2. Top quark discovered (Fermilab news release)
The electron, up-quark and down-quark form the fundamental constituents atoms.

3. Quarks combined in pairs (bosonic hadrons) or triplets (fermionic hadrons) form a variety
of particles (the Hadrons). The common proton and neutron belong to this family. More
exotic particles are also formed:
The energy unit of particle physics is the electron volt (eV), the energy gained by one
electron in crossing a potential difference of one volt. Masses are given in GeV/c2.
(Remember E = mc2 ), where 1 GeV = 109 eV = 1.60 * 10-10 joule. The mass of the proton
is 0.938 GeV/c2 = 1.67*10-27 kg
Figure (left) : A neutron decays to a proton, an electron, and an antineutrino via a virtual
(mediating) W boson. This is neutron beta decay.
Figure (right) : The c and cbar quarks in an eta_c meson annihilate into virtual gluons.
Quark pair production in the gluon cloud sometimes gives a pi+, K0, and K- as the final
state.
Figure (left) : An electron and positron (antielectron) colliding at high energy can
annihilate to produce D+ and D- mesons via a virtual Z boson or a virtual photon.