This article for those who faces for the first time with mass spectrometry, but for obvious reasons they don't want to refer to mass spectrometers as to "black boxes". In this article all mass spectrometers which are used in analytical practice are mentioned. The huge need of analytical practice for very sensitive and selective methods of detection have stimulated the attraction of various mass analyzers by mass spectral laboratories. The concentration of analytes, requirements for limit of detection and sample content define the choice of the device.