The Mass Spectrometry Primer, an 82-page paperback book, covers a wide range of topics related to the most wide spread of modern mass spectrometry practices and answers some frequently asked questions about the use and capabilities of mass spectrometers. Links are also provided to articles for more in-depth reading. The first section examines who uses mass spectrometers, followed by how compounds are ionized in the source to be analyzed by mass spectrometers. A description of the various types of mass spectrometers is followed by a discussion of the important topics of mass accuracy and resolution — or how well we can tell differences between closely related compounds. Chemistry, sample prep, and data handling are considered, as well as the definition of some terms commonly used in the most prevalent forms of MS practice today.