Mass spectrometry has long served as an invaluable tool for detection of type and concentration of chemicals present in carefully-prepared laboratory samples. Mass spectrometry analysis sorts, separates and measures sample ions in relation to instrument magnetic and electronic fields. Recent innovations in the technology have vastly increased the utility of mass spectrometry by allowing for measurement under standard environmental conditions (“ambient”), making the instruments far more portable and requiring little or no sample preparation. Applications of this newer technology range from biomedical, food safety, criminal analysis, and national security, to pollution, and far beyond. This wide array of applications is reflected in an equally wide array of acronyms for the types of ambient ion mass spectrometry. The alphabet soup includes DART (“direct analysis in real time”), DESI (“desorption electrospray ionization”), ASAP (“ambient samples analysis probe”), APPI (“atmospheric-pressure photoionization”), EASI (“easy ambient sonic-spray ionization”), LAESI (“laser ablation electrospray ionization”), ELDI (“electrospray laser desorption ionization”), and “paper spray”, to name just a few of the many. This book is the first to bring together in a single work a collection of chapter-length articles by leaders and practitioners in the field ranging widely through the many types, and serves as an excellent gateway to understanding the benefits and uses of this new technology.