A mass spectrum is a plot of the ion signal as a function of the mass-to-charge ratio. These spectra are used to determine the elemental or isotopic signature of a sample, the masses of particles and of molecules, and to elucidate the chemical identity or structure of molecules and other chemical compounds. Mass spectrometry provides valuable information about the structure of molecular compounds. Organic chemists can use a mass spectrometer to ionize a molecular compound in gaseous form, sort the fragments, and then identify the molecule fragments based on their molecular weights. This journal invites papers that the new field of mass spectrometry by exploring fundamental aspects of ion methods using both the experimental and theoretical approaches.