We present a brief overview of crucial historical stages in creation of superfluidity theory and of the currentudstate of the microscopic theory of superfluidud⁴He. We pay special attention to the role of Bose-Einstein condensatesud(BECs) in understanding of physical mechanisms of superfluidity and identification of quantum mechanicaludstructure ofud⁴He superfluid component below -point, in particular — the possibility that at least two types ofudcondensates may appear and coexist simultaneously in superfluidud⁴He. In this context we discuss the propertiesudof the binary mixtures of BECs and types of excitations, which may appear due to intercomponent interaction inudsuch binary mixtures of condensates. We also discuss current status of investigations of persistent currents in toroidaludoptical traps and present an outlook of our recent findings on this subject.
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