Particle tracks. Conceptual computer illustration depicting the increasing human understanding of particle physics as a head viewing subatomic part- icle tracks (orange). A repeated physics equation and particles (coloured points) are also seen. 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 creates 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.