Matter is simply stuff — anything that takes up space and has mass, from the air you're breathing to the chair you're sitting on to the distant stars. The big question of this branch of physics is deceptively simple: what is everything made of?

The answer is one of the most powerful ideas ever found: everything is built from unimaginably tiny particles. Picture the particle model and suddenly a whole world of puzzles clicks into place — why ice melts, why balloons pop, why some materials stretch and others shatter, and what waits deep inside the atom.

Three branches to explore

Start with matter — solids, liquids and gases, and the particle model that explains how they behave and change. Then see why different materials — metal, rubber, glass — have such different properties. Finally, zoom all the way in to the atom itself, and the astonishing physics of what lies at its core.