Secondary ion mass spectrometry (SIMS) is one of the most sensitive and versatile analytical techniques in existence, and is used in astrophysics, biology, medicine, semiconductors, geology, metallurgy, and in many other areas. It can be used to analyse the nanolayer on the surface of any material, and to map the chemical structure of a sample in 3 dimensions on a scale from nanometers to 10's of micrometres. With the right instrumentation it can depth profile a new semiconductor layer structure with sub-nm depth resolution and parts per billion sensitivity, or date microscopic zircon crystals in rocks from the Pb isotope ratio. It can determine the orientation of a protein molecule on a surface, or examine the absorption of chemical species into tissue cells. Because the technique is much in demand from industry and academic research, there is always a need for instrument and technique development to meet new analytical challenges.