Due to quantum coherence of Bose-Einstein condensate and Coulomb interaction of electrons, superconducting metallic structures comprising small-area (with typical linear dimensions 80–20 nm) tunnel junctions and submicron islands between these junctions enable transport of individual charge carriers, i.e. Cooper pairs carrying charge of 2e. This phenomenon makes it possible to construct electronic devices with record characteristics. Among these devices are supersensitive electrometers operating on the principle of modulation of the Josephson critical current in the Bloch transistor (a two-junction system which central island is equipped by a capacitively coupled gate). Linear arrays of small superconducting tunnel junctions can be used for realization of clocked transfer of individual Cooper pairs. As result, the dc current across the array is equal I=2ef, where f is frequency of the driving signal. This setup can potentially serve as a quantum standard of electrical current. Finally, there is a challenge of using superconducting structures with small tunnel junctions in quantum computing. In particular, the Bloch transistor inserted into small superconducting ring presents a two-level system which ideally suits for being used as solid-state qubit. The theoretical analysis of characteristics of these devices and preliminary results of experiments will be presented.