The Standard Model

Particle physicists believe that matter is built of twelve types of fundamental particle – the building blocks of the universe. These fundamental particles cannot be broken down any further.

Fig: Classification of Elementary Particles according to Standard Model

There are two families of fundamental particles- the quarks and the leptons.
There are six sorts of quarks, six sorts of leptons and four force carriers. Together they make up a theory which is called the Standard Model. The Standard Model explains what the world is and what holds it together.
Most matter on earth is made from a combination of two quarks, called the up and the down quarks and a lepton called the electron.
The up and down quarks form protons and neutrons inside the nucleus of the atom, and the electrons orbit the nucleus to complete the whole atom.
The rest of the twelve fundamental particles are more commonly found in high energy environments, for example in particle accelerator collisions, or right at the start of the universe just after the Big Bang.