Inductively coupled plasma---mass spectrometry is an analytical technique which requires the sample to be introduced to a high temperature plasma, commonly argon, which dissociates molecules and ionizes atoms. The ions are passed into vacuum via a sample and skimmer cone interface, where a lens stack focuses the ion beam into a quadrupole mass spectrometer. Here, the ions are sorted by mass and detected using a scanning electron multiplier. The use of a laser in ICP-MS has allowed the geochemical analysis of small, solid samples to be accomplished. In order to give an insight to the potential of LA-ICP-MS, reference to work published by non-US labs up to the present day is made in outlining the theory and development behind this new and exciting analytical technique.