They think the universe is stuffed with invisible dark matter composed of particles very different from the ones that make up visible matter, and it is the gravity of this dark matter that holds galaxies together.

ECONOMIST: Spotting dark matter, at last

Cosmologists reckon that at least a quarter of the universe is composed of dark matter, a mysterious substance that neither emits nor absorbs light.

WSJ: New Data Boosts Case for Higgs Boson Find

The "concordance" model of the Universe proposes that over 70% is made up of dark energy, with around 25% composed of dark matter and only 5% of normal matter.

BBC: NEWS | Science/Nature | Dark energy tops science class

In particular, every type of particle of which matter is composed has an equal and opposite antiparticle composed of antimatter.

ECONOMIST: Particle physics

According to the standard model these six particles (the flavoured neutrinos and the corresponding electron-like particles) together with another six, the quarks (which make up the protons and neutrons in atomic nuclei), are the irreducible units from which the rest of matter is composed.

ECONOMIST: Neutrinos

This slowly moving clump was composed entirely of sodium atoms, effectively turning light into matter.

BBC: NEWS | Science/Nature | Cool clouds turn light to matter

Delvoye is no stranger to controversy: he is perhaps best known for his work Cloaca, an installation composed of a large machine reproducing the effects of the human digestive system to create, in essence, industrial faecal matter .

BBC: Controversy at the classical Louvre