Particle tracks. Computer illustration of subatomic particle tracks. The particles are seen as coloured points. The tracks result from charged particles moving through a bubble chamber containing a superheated liquid. Ionisation of the liquid by the particles causes it to boil, so that tracks of minute bubbles are left in their wake. Each particle makes a distinct track, such as the spirals made by electrons and positrons. Particle physics has revealed the basic structure of the atoms from which everything is made.