Chip mass spectrometry couples a microfabricated fluidic device directly to a mass spectrometer so that sample handling, separation, reaction, and/or ionization occurs in channels and structures formed on the chip. The chip may incorporate capillary electrophoresis, micro-liquid chromatography, preconcentration, digestion, or mixing, but a mass analyzer remains external and measures the mass-to-charge ratios of ions delivered from the device ^[1]. Coupling commonly uses electrospray from a chip edge, an inserted emitter, or an emitter fabricated as an integral part of the microfluidic substrate; matrix-assisted laser desorption/ionization interfaces form another class ^[2]. The concept is defined by integration of microfluidics with ion generation or sample introduction, not by a unique mass analyzer. It excludes conventional capillary LC–MS lacking a microfabricated device and excludes genomic or optical chips that do not produce ions for mass analysis. Essential features are a microfabricated flow or sample path, a reproducible chip-to-source interface, and transfer of generated ions into the mass spectrometer ^[3].