CERN's main focus is particle physics – the study of the fundamental constituents of matter – but the physics programme at?the laboratory is much broader, ranging from nuclear to high-energy physics, from studies of antimatter to the possible effects of cosmic rays on clouds.

Since the 1970s, particle physicists have described the fundamental structure of matter using an elegant series of equations called the Standard Model. The model describes how everything that they observe in the universe is made from a few basic blocks called fundamental particles, governed by four forces. Physicists at CERN use the world's most powerful particle accelerators and detectors to test the predictions and limits of the Standard Model. Over the years it has explained many experimental results and precisely predicted a range of phenomena, such that today it is considered a well-tested physics theory.

But the model only describes the 4% of the known universe, and questions remain. Will we see a unification of forces at the high energies of the Large Hadron Collider (LHC)? Why is gravity so weak? Why is there more matter than antimatter in the universe? Is there more exotic physics waiting to be discovered at higher energies? Will we discover evidence for a theory called supersymmetry at the LHC? Or understand?the Higgs boson that gives particles mass?

Physicists at CERN are looking for answers to these questions and more – find out more below.

Particles and forces

Scientists at CERN are trying to find out what the smallest building blocks of matter are.

All matter except dark matter is made of molecules, which are themselves made of atoms. Inside the atoms, there are electrons spinning around the nucleus. The nucleus itself is generally made of protons and neutrons but even these are composite objects. Inside the protons and neutrons, we find the quarks, but these appear to be indivisible, just like the electrons.

Quarks and electrons are some of the elementary particles we study at CERN and in other laboratories. But physicists have found more of these elementary particles in various experiments, so many in fact that researchers needed to organize them, just like Mendeleev did with his periodic table.

This is summarized in a concise theoretical model called the Standard Model. Today, we have a very good idea of what matter is made of, how it all holds together and how these particles interact with each other.