Book excerpt: This book highlights the application of Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) for high-resolution surface analysis and characterization of materials. While providing a brief overview of the principles of SIMS, it also provides examples of how dual-beam ToF-SIMS is used to investigate a range of materials systems and properties. Over the years, SIMS instrumentation has dramatically changed since the earliest secondary ion mass spectrometers were first developed. Instruments were once dedicated to either the depth profiling of materials using high-ion-beam currents to analyse near surface to bulk regions of materials (dynamic SIMS), or time-of-flight instruments that produced complex mass spectra of the very outer-most surface of samples, using very low-beam currents (static SIMS). Now, with the development of dual-beam instruments these two very distinct fields now overlap.