Chapter 6 describes examples of practical analytical applications of the superconductor detectors. The superconductor detectors allow surpassing fundamental limits of conventional analytical instrumentsAnalytical instrument. The analytical applications include X-ray spectroscopy and mass spectrometry. The novel analytical results contribute to a wide range of fields, such as dentistryDentistry, molecular biologyMolecular biology, energy-saving societyEnergy-saving society, planetary sciencePlanetary science, and prebiotic organic moleculesPrebiotic organic molecule in space. Potential applications to other fields such as atom probe tomography are also described.