This chapter discusses superconducting states in nature. The absence of resistance is the most remarkable manifestation of the superconducting state. But pair correlation is a general phenomenon that can be manifested in various systems, such as atomic nuclei, where the pairing is manifested in spectra, especially via the odd–even effect (the presence of unpaired nucleons makes it possible for nuclei to absorb a lower frequency of radiation than nuclei with an even number of nucleons can) and in the amplitudes of their momenta of inertia, which are smaller than in a rigid model. Another system, the neutron star, has an entirely different spatial scale. However, its low heat capacity leads to its rapid cooling, and the existence of a vortex structure affects the star’s rotation period. Finally, biologically active systems contain delocalised electrons, and the formation of electron pairs affects charge transfer, which is similar to Josephson tunnelling.