In physics, atomic spectroscopy is the study of the electromagnetic radiation absorbed and emitted by atoms. Since unique elements have unique emission spectra, atomic spectroscopy is applied for determination of elemental compositions. It can be divided by atomization source or by the type of spectroscopy used.  In the latter case, the main division is between optical and mass spectrometry.  Mass spectrometry generally gives significantly better analytical performance, but is also significantly more complex.  This complexity translates into higher purchase costs, higher operational costs, more operator training, and a greater number of components that can potentially fail.  Because optical spectroscopy is often less expensive and has performance adequate for many tasks, it is far more common. Atomic absorption spectrometers are one of the most commonly sold and used analytical devices.